Method and apparatus for explicit csi reporting in advanced wireless communication systems

ABSTRACT

A method for a channel state information (CSI) feedback comprises receiving CSI feedback configuration information for the CSI feedback including a spatial channel information indicator based on a linear combination (LC) codebook, wherein the spatial channel information comprises at least one of a downlink channel matrix, a covariance matrix of the downlink channel matrix, or at least one eigenvector of the covariance matrix of the downlink channel matrix; deriving the spatial channel information indicator using the LC codebook that indicates a weighted linear combination of a plurality of basis vectors or a plurality of basis matrices as a representation of at least one of a downlink channel matrix, a covariance matrix of the downlink channel matrix, or at least one eigenvector of the covariance matrix of the downlink channel matrix; and transmitting over an uplink channel, the CSI feedback including the spatial channel information indicator.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 17/222,744 filed Apr. 5, 2021 and entitled “Methodand Apparatus for Explicit CSI Reporting in Advanced WirelessCommunication Systems,” now U.S. Pat. No. 11,483,040, which is acontinuation of U.S. Non-Provisional patent application Ser. No.16/684,385 filed Nov. 14, 2019 and entitled “Method and Apparatus forExplicit CSI Reporting in Advanced Wireless Communication Systems,” nowU.S. Pat. No. 10,972,161, which is a continuation of U.S.Non-Provisional patent application Ser. No. 15/490,561 filed Apr. 18,2017 and entitled “Method and Apparatus for Explicit CSI Reporting inAdvanced Wireless Communication Systems,” now U.S. Pat. No. 10,659,118and claims priority to: U.S. Provisional Patent Application No.62/324,604 filed Apr. 19, 2016 and entitled “Method and Apparatus forExplicit CSI reporting in Advanced Wireless Communication Systems;” U.S.Provisional Patent Application No. 62/351,465 filed Jun. 17, 2016 andentitled “Hybrid CSI Reporting for MIMO Wireless Communication Systems;”U.S. Provisional Patent Application No. 62/353,781, filed on Jun. 23,2016, entitled “Method and Apparatus for Explicit CSI reporting inAdvanced Wireless Communication Systems;” U.S. Provisional PatentApplication No. 62/377,711 filed Aug. 22, 2016 and entitled “Hybrid CSIReporting for MIMO Wireless Communication Systems;” and U.S. ProvisionalPatent Application No. 62/378,578 filed Aug. 23, 2016 and entitled“Hybrid CSI Reporting for MIMO Wireless Communication Systems.” Thecontent of the above-identified patent documents are incorporated hereinby reference.

TECHNICAL FIELD

The present application relates generally to channel state information(CSI) reporting operation in advanced wireless communication systems.More specifically, this disclosure relates to advanced CSI reportingbased on linear combination codebook wherein the advanced CSI comprisesat least one of a downlink channel matrix, a covariance matrix of thedownlink channel matrix, or at least one eigenvector of the covariancematrix of the downlink channel matrix.

BACKGROUND

Understanding and correctly estimating the channel in an advancewireless communication system between a user equipment (UE) and an eNodeB (eNB) is important for efficient and effective wireless communication.In order to correctly estimate the channel conditions, the UE may report(e.g., feedback) information about channel measurement, e.g., CSI, tothe eNB. With this information about the channel, the eNB is able toselect appropriate communication parameters to efficiently andeffectively perform wireless data communication with the UE. However,with increase in the numbers of antennas and channel paths of wirelesscommunication devices, so too has the amount of feedback increased thatmay be needed to ideally estimate the channel. This additionally-desiredchannel feedback may create additional overheads, thus reducing theefficiency of the wireless communication, for example, decrease the datarate.

SUMMARY

The present disclosure relates to a pre-5^(th)-Generation (5G) or 5Gcommunication system to be provided for supporting higher data ratesbeyond 4^(th)-Generation (4G) communication system such as long termevolution (LTE). Embodiments of the present disclosure provide anadvanced CSI reporting based on linear combination codebook for MIMOwireless communication systems wherein advanced CSI comprises at leastone of a downlink channel matrix, a covariance matrix of the downlinkchannel matrix, or at least one eigenvector of the covariance matrix ofthe downlink channel matrix.

In one embodiment, a user equipment (UE) for a channel state information(CSI) feedback in an advanced communication system is provided. The UEcomprises a transceiver configured to receive, via a higher layersignaling from a base station (BS), CSI feedback configurationinformation for the CSI feedback including a spatial channel informationindicator based on a linear combination (LC) codebook, wherein thespatial channel information indicator comprises at least one of adownlink channel matrix, a covariance matrix of the downlink channelmatrix, or at least one eigenvector of the covariance matrix of thedownlink channel matrix. The UE further comprises at least one processorconfigured to derive the spatial channel information indicator using theLC codebook that indicates a weighted linear combination of a pluralityof basis vectors or a plurality of basis matrices as a representation ofat least one of a downlink channel matrix, a covariance matrix of thedownlink channel matrix, or at least one eigenvector of the covariancematrix of the downlink channel matrix, wherein, the transceiver isfurther configured to transmit, to the BS, over an uplink channel, theCSI feedback including the spatial channel information indicator.

In another embodiment, a base station (BS) for a channel stateinformation (CSI) feedback in an advanced communication system isprovided. The BS comprises a transceiver configured to transmit, via ahigher layer signaling to a user equipment (UE), CSI feedbackconfiguration information for the CSI feedback including a spatialchannel information indicator based on a linear combination (LC)codebook, wherein the spatial channel information indicator comprises atleast one of a downlink channel matrix, a covariance matrix of thedownlink channel matrix, or at least one eigenvector of the covariancematrix of the downlink channel matrix; and receive, from the UE, over anuplink channel, the CSI feedback including the spatial channelinformation indicator, wherein the spatial channel information indicatoris derived using the LC codebook that indicates a weighted linearcombination of a plurality of basis vectors or a plurality of basismatrices as a representation of at least one of a downlink channelmatrix, a covariance matrix of the downlink channel matrix, or at leastone eigenvector of the covariance matrix of the downlink channel matrix.

In yet another embodiment, a method for a channel state information(CSI) feedback in an advanced communication system is provided. Themethod comprises receiving, via a higher layer signaling from a basestation (BS), CSI feedback configuration information for the CSIfeedback including a spatial channel information indicator based on alinear combination (LC) codebook, wherein the spatial channelinformation indicator comprises at least one of a downlink channelmatrix, a covariance matrix of the downlink channel matrix, or at leastone eigenvector of the covariance matrix of the downlink channel matrix;deriving, by a user equipment (UE), the spatial channel informationindicator using the LC codebook that indicates a weighted linearcombination of a plurality of basis vectors or a plurality of basismatrices as a representation of at least one of a downlink channelmatrix, a covariance matrix of the downlink channel matrix, or at leastone eigenvector of the covariance matrix of the downlink channel matrix;and transmitting, to the BS, over an uplink channel, the CSI feedbackincluding the spatial channel information indicator.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and derivatives referto any direct or indirect communication between two or more elements,whether or not those elements are in physical contact with one another.The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

Aspects, features, and advantages of the present disclosure are readilyapparent from the following detailed description, simply by illustratinga number of particular embodiments and implementations, including thebest mode contemplated for carrying out the present disclosure. Thepresent disclosure is also capable of other and different embodiments,and its several details can be modified in various obvious respects, allwithout departing from the spirit and scope of the present disclosure.Accordingly, the drawings and description are to be regarded asillustrative in nature, and not as restrictive. The present disclosureis illustrated by way of example, and not by way of limitation, in thefigures of the accompanying drawings.

In the following, for brevity, both FDD and TDD are considered as theduplex method for both DL and UL signaling.

Although exemplary descriptions and embodiments to follow assumeorthogonal frequency division multiplexing (OFDM) or orthogonalfrequency division multiple access (OFDMA), this present disclosure canbe extended to other OFDM-based transmission waveforms or multipleaccess schemes such as filtered OFDM (F-OFDM).

This present disclosure covers several components which can be used inconjunction or in combination with one another, or can operate asstandalone schemes

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure;

FIG. 2 illustrates an example eNodeB (eNB) according to embodiments ofthe present disclosure;

FIG. 3 illustrates an example user equipment (UE) according toembodiments of the present disclosure;

FIG. 4A illustrates a high-level diagram of an orthogonal frequencydivision multiple access transmit path according to embodiments of thepresent disclosure;

FIG. 4B illustrates a high-level diagram of an orthogonal frequencydivision multiple access receive path according to embodiments of thepresent disclosure;

FIG. 5 illustrates an example structure for a downlink (DL) subframeaccording to embodiments of the present disclosure;

FIG. 6 illustrates an example transmission structure of an uplink (UL)subframe according to embodiments of the present disclosure;

FIG. 7 illustrates an example transmitter block diagram for a physicaldownlink shared channel (PDSCH) subframe according to embodiments of thepresent disclosure;

FIG. 8 illustrates an example receiver block diagram for a PDSCHsubframe according to embodiments of the present disclosure;

FIG. 9 illustrates an example transmitter block diagram for a physicaluplink shared channel (PUSCH) subframe according to embodiments of thepresent disclosure;

FIG. 10 illustrates an example receiver block diagram for a physicaluplink shared channel (PUSCH) in a subframe according to embodiments ofthe present disclosure;

FIG. 11 illustrates an example configuration of a two dimensional (2D)array according to embodiments of the present disclosure;

FIG. 12 illustrates an example dual-polarized antenna port layouts for{2, 4, 8, 12, 16} ports according to embodiments of the presentdisclosure;

FIG. 13 illustrates example dual-polarized antenna port layouts for {20,24, 28, 32} ports according to embodiments of the present disclosure;

FIG. 14 illustrates example explicit channel state information (CSI)feedback framework according to embodiments of the present disclosure;

FIG. 15 illustrates example orthogonal bases according to embodiments ofthe present disclosure;

FIG. 16 illustrates an example implicit or explicit CSI based on a rankaccording to embodiments of the present disclosure;

FIG. 17 illustrates an example partial port explicit feedback accordingto embodiments of the present disclosure;

FIG. 18 illustrates example W₁ codebook alternatives according toembodiments of the present disclosure;

FIG. 19 illustrates example master beam groups according to embodimentsof the present disclosure;

FIG. 20 illustrates an example beam selection according to embodimentsof the present disclosure;

FIG. 21 illustrates an example frequency domain representationalternatives according to embodiments of the present disclosure;

FIG. 22 illustrates an example W₁ beams or basis according toembodiments of the present disclosure;

FIG. 23 illustrates an example Class A CSI feedback scheme according toembodiments of the present disclosure;

FIG. 24 illustrates an example Class B CSI feedback scheme according toembodiments of the present disclosure;

FIG. 25 illustrates an example hybrid configuration forCodebook-Config=1 according to embodiments of the present disclosure;

FIG. 26 illustrates an example hybrid configuration forCodebook-Config=2, 3, and 4 according to embodiments of the presentdisclosure;

FIG. 27 illustrates an example hybrid CSI reporting according toembodiments of the present disclosure;

FIG. 28 illustrates an example codebook types for Class B K₁=2eMIMO-Type according to embodiments of the present disclosure;

FIG. 29 illustrates a table for a Codebook-Config parameter to rank 1beam grouping mapping according to embodiments of the presentdisclosure; and

FIG. 30 illustrates a table for an alternate Codebook-Config to beamgroup mapping according to embodiments of the present disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 30 , discussed below, and the various embodiments usedto describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artmay understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

The following documents and standards descriptions are herebyincorporated by reference into the present disclosure as if fully setforth herein: 3GPP TS 36.211 v14.2.0, “E-UTRA, Physical channels andmodulation” (REF1); 3GPP TS 36.212 v14.2.0, “E-UTRA, Multiplexing andChannel coding” (REF2); 3GPP TS 36.213 v14.2.0, “E-UTRA, Physical LayerProcedures” (REF3); 3GPP TS 36.321 v14.2.0, “E-UTRA, Medium AccessControl (MAC) protocol specification” (REF4); 3GPP TS 36.331 v14.2.0,“E-UTRA, Radio Resource Control (RRC) protocol specification” (REF5);and RP-160623, “New WID Proposal: Enhancements on Full-Dimension (FD)MIMO for LTE,” Samsung (REF6).

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a ‘Beyond 4G Network’ or a‘Post LTE System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission coverage, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques and the like arediscussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul communication, moving network,cooperative communication, coordinated multi-points (CoMP) transmissionand reception, interference mitigation and cancellation and the like.

In the 5G system, hybrid frequency shift keying and quadrature amplitudemodulation (FQAM) and sliding window superposition coding (SWSC) as anadaptive modulation and coding (AMC) technique, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

FIGS. 1-4B below describe various embodiments implemented in wirelesscommunications systems and with the use of OFDM or OFDMA communicationtechniques. The descriptions of FIGS. 1-3 are not meant to implyphysical or architectural limitations to the manner in which differentembodiments may be implemented. Different embodiments of the presentdisclosure may be implemented in any suitably-arranged communicationssystem.

FIG. 1 illustrates an example wireless network 100 according toembodiments of the present disclosure. The embodiment of the wirelessnetwork 100 shown in FIG. 1 is for illustration only. Other embodimentsof the wireless network 100 could be used without departing from thescope of this disclosure.

As shown in FIG. 1 , the wireless network 100 includes an eNB 101, aneNB 102, and an eNB 103. The eNB 101 communicates with the eNB 102 andthe eNB 103. The eNB 101 also communicates with at least one network130, such as the Internet, a proprietary Internet Protocol (IP) network,or other data network.

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which may belocated in a small business (SB); a UE 112, which may be located in anenterprise (E); a UE 113, which may be located in a WiFi hotspot (HS); aUE 114, which may be located in a first residence (R); a UE 115, whichmay be located in a second residence (R); and a UE 116, which may be amobile device (M), such as a cell phone, a wireless laptop, a wirelessPDA, or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 maycommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, WiFi, or other wireless communication techniques.

Depending on the network type, the term “base station” or “BS” can referto any component (or collection of components) configured to providewireless access to a network, such as transmit point (TP),transmit-receive point (TRP), an enhanced base station (eNodeB or eNB),gNB, a macrocell, a femtocell, a WiFi access point (AP), or otherwirelessly enabled devices. Base stations may provide wireless access inaccordance with one or more wireless communication protocols, e.g., 5G3GPP New Radio Interface/Access (NR), long term evolution (LTE), LTEadvanced (LTE-A), High Speed Packet Access (HSPA), Wi-Fi802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “eNodeB”and “eNB” are used in this patent document to refer to networkinfrastructure components that provide wireless access to remoteterminals. Also, depending on the network type, other well-known termsmay be used instead of “user equipment” or “UE,” such as “mobilestation,” “subscriber station,” “remote terminal,” “wireless terminal,”or “user device.” For the sake of convenience, the terms “userequipment” and “UE” are used in this patent document to refer to remotewireless equipment that wirelessly accesses an eNB, whether the UE is amobile device (such as a mobile telephone or smartphone) or is normallyconsidered a stationary device (such as a desktop computer or vendingmachine).

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, may have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of the UEs 111-116include circuitry, programing, or a combination thereof, for efficientCSI reporting on an uplink channel in an advanced wireless communicationsystem. In certain embodiments, and one or more of the eNBs 101-103includes circuitry, programing, or a combination thereof, for receivingefficient CSI reporting on an uplink channel in an advanced wirelesscommunication system.

Although FIG. 1 illustrates one example of a wireless network 100,various changes may be made to FIG. 1 . For example, the wirelessnetwork 100 could include any number of eNBs and any number of UEs inany suitable arrangement. Also, the eNB 101 could communicate directlywith any number of UEs and provide those UEs with wireless broadbandaccess to the network 130. Similarly, each eNB 102-103 could communicatedirectly with the network 130 and provide UEs with direct wirelessbroadband access to the network 130. Further, the eNBs 101, 102, and/or103 could provide access to other or additional external networks, suchas external telephone networks or other types of data networks.

FIG. 2 illustrates an example eNB 102 according to embodiments of thepresent disclosure. The embodiment of the eNB 102 illustrated in FIG. 2is for illustration only, and the eNBs 101 and 103 of FIG. 1 could havethe same or similar configuration. However, eNBs come in a wide varietyof configurations, and FIG. 2 does not limit the scope of thisdisclosure to any particular implementation of an eNB.

As shown in FIG. 2 , the eNB 102 includes multiple antennas 205 a-205 n,multiple RF transceivers 210 a-210 n, transmit (TX) processing circuitry215, and receive (RX) processing circuitry 220. The eNB 102 alsoincludes a controller/processor 225, a memory 230, and a backhaul ornetwork interface 235.

The RF transceivers 210 a-210 n receive, from the antennas 205 a-205 n,incoming RF signals, such as signals transmitted by UEs in the network100. The RF transceivers 210 a-210 n down-convert the incoming RFsignals to generate IF or baseband signals. The IF or baseband signalsare sent to the RX processing circuitry 220, which generates processedbaseband signals by filtering, decoding, and/or digitizing the basebandor IF signals. The RX processing circuitry 220 transmits the processedbaseband signals to the controller/processor 225 for further processing.

In some embodiment, the RF transceivers 210 a-210 n is capable oftransmitting, via a higher layer signaling to a user equipment (UE), CSIfeedback configuration information for the CSI feedback including aspatial channel information indicator based on a linear combination (LC)codebook, wherein the spatial channel information indicator comprises atleast one of a downlink channel matrix, a covariance matrix of thedownlink channel matrix, or at least one eigenvector of the covariancematrix of the downlink channel matrix; and receiving, from the UE, overan uplink channel, the CSI feedback including the spatial channelinformation indicator, wherein the spatial channel information indicatoris derived using the LC codebook that indicates a weighted linearcombination of a plurality of basis vectors or a plurality of basismatrices as a representation of at least one of a downlink channelmatrix, a covariance matrix of the downlink channel matrix, or at leastone eigenvector of the covariance matrix of the downlink channel matrix.

In such embodiments, the spatial channel information indicatorcorresponds to a precoding matrix indicator (PMI) comprising a first PMIi₁ to indicate at least one of the plurality of basis vectors or theplurality of basis matrices, and a second PMI i₂ to indicate weights tocombine the plurality of basis vectors or the plurality of basismatrices.

In such embodiments, the spatial channel information indicator comprisesthe at least one eigenvector corresponding to at least one transmiteigenvector derived using an eigen decomposition of an P×P transmitcovariance matrix of an P×R downlink channel matrix, where P is a numberof antenna ports at the BS and R is a number of antenna ports at the UE,and wherein the at least one transmit eigenvector is represented as thefollowing weighted linear combination of the plurality of basis vectors:e_(T,1)≈Σ_(l=0) ^(L) ^(T) ⁻¹c_(T,l)b_(T,l) where b_(T,l) is a transmitbasis vector, c_(T,l) is an l-th transmit weight, and L_(T) is a numberof a plurality of transmit basis vectors.

In such embodiments, the spatial channel information indicator comprisesthe at least one eigenvector corresponding to at least one receiveeigenvector derived using an eigen decomposition of an R×R receivecovariance matrix of an P×R downlink channel matrix, where P is a numberof antenna ports at the BS and R is a number of antenna ports at the UE,and wherein the at least one receive eigenvector is represented as thefollowing weighted linear combination of the plurality of basis vectors:e_(R,1)≈Σ_(l=0) ^(L) ^(R) ⁻¹c_(R,l)b_(R,l) where b_(R,l) is a receivebasis vector, c_(R,l), is an l-th receive weight, and L_(R) is a numberof a plurality of receive basis vectors.

In such embodiments, the spatial channel information indicator comprisesat least one eigenvector corresponding to at least one transmit and atleast one receive eigenvectors that are jointly derived using an eigendecomposition of an P×P transmit covariance matrix and an R×R receivecovariance matrix of an P×R downlink channel matrix, where P is a numberof antenna ports at the BS and R is a number of antenna ports at the UE,and wherein the jointly derived at least one transmit and at least onereceive eigenvectors are represented as the following weighted linearcombination of the plurality of basis vectors: e_(T,1)e_(R,1)^(H)≈Σ_(l=0) ^(L-1)c_(l)b_(T,l)b_(R,l) where b_(T,l) is a transmit basisvector, L is a number of a plurality of transmit and receive basisvectors, b_(R,l) is a receive basis vector, c_(l) is an l-th weight.

In such embodiments, the spatial channel information indicator comprisesat least one of a transmit covariance matrix or a receive covariancematrix based on the downlink channel matrix, wherein the transmit andreceive covariance matrices are represented as the following weightedlinear combination of the plurality of basis matrices:

${{E_{T} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{k}^{(I)} \right)\left( H_{k}^{(I)} \right)^{H}} \right)}} \approx {\sum_{l = 0}^{L_{T} - 1}{c_{T,l}b_{T,l}b_{T,l}^{H}}}}};}{{{and}E_{R}} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{k}^{(I)} \right)^{H}\left( H_{k}^{(I)} \right)} \right)}} \approx {\sum_{l = 0}^{L_{R} - 1}{c_{R,l}b_{R,l}b_{R,l}^{H}}}}}$

where f is a set of frequency subcarriers, H_(k) ^((I)) is a P×Rdownlink channel matrix at a frequency subcarrier k in the set f, E_(T)is a transmit covariance matrix, b_(T,l)b_(T,l) ^(H) is a transmit basismatrix, c_(T,l) is an l-th transmit weight, L_(T) is a number of aplurality of transmit basis matrices, E_(R) is a receive covariancematrix, b_(R,l)b_(R,l) ^(H) is a receive basis matrix, C_(R,l) is anl-th receive weight, and L_(R) is a number of a plurality of receivebasis matrices.

The TX processing circuitry 215 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 225. The TX processing circuitry 215 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 210 a-210 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 215 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 205 a-205 n.

The controller/processor 225 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 225 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 210 a-210 n, the RX processing circuitry 220, andthe TX processing circuitry 215 in accordance with well-knownprinciples. The controller/processor 225 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. For instance, the controller/processor 225 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 205 a-205 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the eNB 102 by thecontroller/processor 225. In some embodiments, the controller/processor225 includes at least one microprocessor or microcontroller. Asdescribed in more detail below, the eNB 102 may include circuitry,programing, or a combination thereof for processing of CSI reporting onan uplink channel. For example, controller/processor 225 can beconfigured to execute one or more instructions, stored in memory 230,that are configured to cause the controller/processor to process vectorquantized feedback components such as channel coefficients.

The controller/processor 225 is also capable of executing programs andother processes resident in the memory 230, such as an OS. Thecontroller/processor 225 can move data into or out of the memory 230 asrequired by an executing process.

The controller/processor 225 is also coupled to the backhaul or networkinterface 235. The backhaul or network interface 235 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 235 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 235 could allow the eNB102 to communicate with other eNBs over a wired or wireless backhaulconnection. When the eNB 102 is implemented as an access point, theinterface 235 could allow the eNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 235 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

The memory 230 is coupled to the controller/processor 225. Part of thememory 230 could include a RAM, and another part of the memory 230 couldinclude a Flash memory or other ROM.

Although FIG. 2 illustrates one example of eNB 102, various changes maybe made to FIG. 2 . For example, the eNB 102 could include any number ofeach component shown in FIG. 2 . As a particular example, an accesspoint could include a number of interfaces 235, and thecontroller/processor 225 could support routing functions to route databetween different network addresses. As another particular example,while shown as including a single instance of TX processing circuitry215 and a single instance of RX processing circuitry 220, the eNB 102could include multiple instances of each (such as one per RFtransceiver). Also, various components in FIG. 2 could be combined,further subdivided, or omitted and additional components could be addedaccording to particular needs.

FIG. 3 illustrates an example UE 116 according to embodiments of thepresent disclosure. The embodiment of the UE 116 illustrated in FIG. 3is for illustration only, and the UEs 111-115 of FIG. 1 could have thesame or similar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3 does not limit the scope of this disclosureto any particular implementation of a UE.

As shown in FIG. 3 , the UE 116 includes an antenna 305, a radiofrequency (RF) transceiver 310, TX processing circuitry 315, amicrophone 320, and receive (RX) processing circuitry 325. The UE 116also includes a speaker 330, a processor 340, an input/output (I/O)interface (IF) 345, a touchscreen 350, a display 355, and a memory 360.The memory 360 includes an operating system (OS) 361 and one or moreapplications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by an eNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the processor340 for further processing (such as for web browsing data).

In some embodiments, the RF transceiver 310 is capable of receiving, viaa higher layer signaling from a base station (BS), CSI feedbackconfiguration information for the CSI feedback including a spatialchannel information indicator based on a linear combination (LC)codebook, wherein the spatial channel information indicator comprises atleast one of a downlink channel matrix, a covariance matrix of thedownlink channel matrix, or at least one eigenvector of the covariancematrix of the downlink channel matrix; and transmitting, to the BS, overan uplink channel, the CSI feedback including the spatial channelinformation indicator.

In such embodiments, the spatial channel information indicatorcorresponds to a precoding matrix indicator (PMI) comprising a first PMIi₁ to indicate at least one of the plurality of basis vectors or theplurality of basis matrices, and a second PMI i₂ to indicate weights tocombine the plurality of basis vectors or the plurality of basismatrices.

In such embodiments, the spatial channel information indicator comprisesthe at least one eigenvector corresponding to at least one transmiteigenvector derived using an eigen decomposition of an P×P transmitcovariance matrix of an P×R downlink channel matrix, where P is a numberof antenna ports at the BS and R is a number of antenna ports at the UE,and wherein the at least one transmit eigenvector is represented as thefollowing weighted linear combination of the plurality of basis vectors:e_(T,1)≈Σ_(l=0) ^(L) ^(T) ⁻¹c_(T,l)b_(T,l) where b_(T,l) is a transmitbasis vector, c_(T,l) is an l-th transmit weight, and L_(T) is a numberof a plurality of transmit basis vectors.

In such embodiments, the spatial channel information indicator comprisesthe at least one eigenvector corresponding to at least one receiveeigenvector derived using an eigen decomposition of an R×R receivecovariance matrix of an P×R downlink channel matrix, where P is a numberof antenna ports at the BS and R is a number of antenna ports at the UE,and wherein the at least one receive eigenvector is represented as thefollowing weighted linear combination of the plurality of basis vectors:e_(R,1)≈Σ_(l=0) ^(L) ^(R) ⁻¹c_(R,l)b_(R,l) where b_(R,l), is a receivebasis vector, c_(R,l) is an l-th receive weight, and L_(R) is a numberof a plurality of receive basis vectors.

In such embodiments, the spatial channel information indicator comprisesat least one eigenvector corresponding to at least one transmit and atleast one receive eigenvectors that are jointly derived using an eigendecomposition of an P×P transmit covariance matrix and an R×R receivecovariance matrix of an P×R downlink channel matrix, where P is a numberof antenna ports at the BS and R is a number of antenna ports at the UE,and wherein the jointly derived at least one transmit and at least onereceive eigenvectors are represented as the following weighted linearcombination of the plurality of basis vectors: e_(T,1)e_(R,1)^(H)≈Σ_(l=0) ^(L-1)c_(l)b_(T,l)b_(R,l) ^(H) where b_(T,l) is a transmitbasis vector, L is a number of a plurality of transmit and receive basisvectors, b_(R,l) is a receive basis vector, c_(l) is an l-th weight.

In such embodiments, the spatial channel information indicator comprisesat least one of a transmit covariance matrix or a receive covariancematrix based on the downlink channel matrix, wherein the transmit andreceive covariance matrices are represented as the following weightedlinear combination of the plurality of basis matrices:

${{E_{T} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{k}^{(I)} \right)\left( H_{k}^{(I)} \right)^{H}} \right)}} \approx {\sum_{l = 0}^{L_{T} - 1}{c_{T,l}b_{T,l}b_{T,l}^{H}}}}};}{{{and}E_{R}} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{k}^{(I)} \right)^{H}\left( H_{k}^{(I)} \right)} \right)}} \approx {\sum_{l = 0}^{L_{R} - 1}{c_{R,l}b_{R,l}b_{R,l}^{H}}}}}$

where f is a set of frequency subcarriers, H_(k) ^((l)) is a P×Rdownlink channel matrix at a frequency subcarrier k in the set f, E_(T)is a transmit covariance matrix, b_(T,l)b_(T,l) ^(H) is a transmit basismatrix, c_(T,l) is an l-th transmit weight, L_(T) is a number of aplurality of transmit basis matrices, E_(R) is a receive covariancematrix, b_(R,l)b_(R,l) ^(H) is a receive basis matrix, c_(R,l) is anl-th receive weight, and L_(R) is a number of a plurality of receivebasis matrices. In some embodiments, the RF transceiver 310 is capableof transmitting, over the uplink channel, the CSI feedback including themultiple spatial channel information indicators in multiple timeinstances where each spatial channel information indicator correspondsthe CSI for a subset of antenna ports at the BS.

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS 361 stored in the memory 360 in order tocontrol the overall operation of the UE 116. For example, the processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as processes for CSI reportingon an uplink channel. The processor 340 can move data into or out of thememory 360 as required by an executing process. In some embodiments, theprocessor 340 is configured to execute the applications 362 based on theOS 361 or in response to signals received from eNBs or an operator. Theprocessor 340 is also coupled to the I/O interface 345, which providesthe UE 116 with the ability to connect to other devices, such as laptopcomputers and handheld computers. The I/O interface 345 is thecommunication path between these accessories and the processor 340.

In some embodiments, the processor 340 is also capable of deriving, by auser equipment (UE), the spatial channel information indicator using theLC codebook that indicates a weighted linear combination of a pluralityof basis vectors or a plurality of basis matrices as a representation ofat least one of a downlink channel matrix, a covariance matrix of thedownlink channel matrix, or at least one eigenvector of the covariancematrix of the downlink channel matrix, wherein, the transceiver isfurther configured to transmit, to the BS, over an uplink channel, theCSI feedback including the spatial channel information indicator.

In such embodiments, spatial channel information indicator correspondsto a precoding matrix indicator (PMI) comprising a first PMI i₁ toindicate at least one of the plurality of basis vectors or the pluralityof basis matrices, and a second PMI i₂ to indicate weights to combinethe plurality of basis vectors or the plurality of basis matrices.

In such embodiments, the spatial channel information indicator comprisesthe at least one eigenvector corresponding to at least one transmiteigenvector derived using an eigen decomposition of an P×P transmitcovariance matrix of an P×R downlink channel matrix, where P is a numberof antenna ports at the BS and R is a number of antenna ports at the UE,and wherein the at least one transmit eigenvector is represented as thefollowing weighted linear combination of the plurality of basis vectors:e_(T,1)≈Σ_(l=0) ^(L) ^(T) ⁻¹c_(T,l)b_(T,l) where b_(T,l) is a transmitbasis vector, c_(T,l) is an l-th transmit weight, and L_(T) is a numberof a plurality of transmit basis vectors.

In such embodiments, the spatial channel information indicator comprisesthe at least one eigenvector corresponding to at least one receiveeigenvector derived using an eigen decomposition of an R×R receivecovariance matrix of an P×R downlink channel matrix, where P is a numberof antenna ports at the BS and R is a number of antenna ports at the UE,and wherein the at least one receive eigenvector is represented as thefollowing weighted linear combination of the plurality of basis vectors:e_(R,1)≈Σ_(l=0) ^(L) ^(R) ⁻¹c_(R,l)b_(R,l) where b_(R,l) is a receivebasis vector, c_(R,l) is an l-th receive weight, and L_(R) is a numberof a plurality of receive basis vectors.

In such embodiments, the spatial channel information indicator comprisesat least one eigenvector corresponding to at least one transmit and atleast one receive eigenvectors that are jointly derived using an eigendecomposition of an P×P transmit covariance matrix and an R×R receivecovariance matrix of an P×R downlink channel matrix, where P is a numberof antenna ports at the BS and R is a number of antenna ports at the UE,and wherein the jointly derived at least one transmit and at least onereceive eigenvectors are represented as the following weighted linearcombination of the plurality of basis vectors: e_(T,1)e_(R,1)^(H)≈Σ_(l=0) ^(L-1)c_(l)b_(T,l)b_(R,l) ^(H) where b_(T,l) is a transmitbasis vector, L is a number of a plurality of transmit and receive basisvectors, b_(R,l) is a receive basis vector, c_(l) is an l-th weight.

In such embodiments, the spatial channel information indicator comprisesat least one of a transmit covariance matrix or a receive covariancematrix based on the downlink channel matrix, wherein the transmit andreceive covariance matrices are represented as the following weightedlinear combination of the plurality of basis matrices:

${{E_{T} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{k}^{(I)} \right)\left( H_{k}^{(I)} \right)^{H}} \right)}} \approx {\sum_{l = 0}^{L_{T} - 1}{c_{T,l}b_{T,l}b_{T,l}^{H}}}}};}{{{and}E_{R}} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{k}^{(I)} \right)^{H}\left( H_{k}^{(I)} \right)} \right)}} \approx {\sum_{l = 0}^{L_{R} - 1}{c_{R,l}b_{R,l}b_{R,l}^{H}}}}}$

where f is a set of frequency subcarriers, H_(k) ^((I)) is a P×Rdownlink channel matrix at a frequency subcarrier k in the set f, E_(T)is a transmit covariance matrix, b_(T,l)b_(T,l) ^(H) is a transmit basismatrix, c_(T,l) is an l-th transmit weight, L_(T) is a number of aplurality of transmit basis matrices, E_(R) is a receive covariancematrix, b_(R,l)b_(R,l) ^(H) is a receive basis matrix, c_(R,l) is anl-th receive weight, and L_(R) is a number of a plurality of receivebasis matrices.

In some embodiments, the processor 340 is also capable of partitioningthe spatial channel information indicator into multiple spatial channelinformation indicators each of which corresponds to a subset of antennaports at the BS and comprises at least one of a downlink channel matrix,a covariance matrix of the downlink channel matrix, or at least oneeigenvector of the covariance matrix of the downlink channel matrix,wherein the downlink channel matrix corresponds to the subset of antennaports at the BS.

The processor 340 is also coupled to the touchscreen 350 and the display355. The operator of the UE 116 can use the touchscreen 350 to enterdata into the UE 116. The display 355 may be a liquid crystal display,light emitting diode display, or other display capable of rendering textand/or at least limited graphics, such as from web sites.

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

Although FIG. 3 illustrates one example of UE 116, various changes maybe made to FIG. 3 . For example, various components in FIG. 3 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, theprocessor 340 could be divided into multiple processors, such as one ormore central processing units (CPUs) and one or more graphics processingunits (GPUs). Also, while FIG. 3 illustrates the UE 116 configured as amobile telephone or smartphone, UEs could be configured to operate asother types of mobile or stationary devices.

FIG. 4A is a high-level diagram of transmit path circuitry 400. Forexample, the transmit path circuitry 400 may be used for an orthogonalfrequency division multiple access (OFDMA) communication. FIG. 4B is ahigh-level diagram of receive path circuitry 450. For example, thereceive path circuitry 450 may be used for an orthogonal frequencydivision multiple access (OFDMA) communication. In FIGS. 4A and 4B, fordownlink communication, the transmit path circuitry 400 may beimplemented in a base station (eNB) 102 or a relay station, and thereceive path circuitry 450 may be implemented in a user equipment (e.g.user equipment 116 of FIG. 1 ). In other examples, for uplinkcommunication, the receive path circuitry 450 may be implemented in abase station (e.g. eNB 102 of FIG. 1 ) or a relay station, and thetransmit path circuitry 400 may be implemented in a user equipment (e.g.user equipment 116 of FIG. 1 ).

Transmit path circuitry 400 comprises channel coding and modulationblock 405, serial-to-parallel (S-to-P) block 410, Size N Inverse FastFourier Transform (IFFT) block 415, parallel-to-serial (P-to-S) block420, add cyclic prefix block 425, and up-converter (UC) 430. Receivepath circuitry 450 comprises down-converter (DC) 455, remove cyclicprefix block 460, serial-to-parallel (S-to-P) block 465, Size N FastFourier Transform (FFT) block 470, parallel-to-serial (P-to-S) block475, and channel decoding and demodulation block 480.

At least some of the components in FIGS. 4A and 4B may be implemented insoftware, while other components may be implemented by configurablehardware or a mixture of software and configurable hardware. Inparticular, it is noted that the FFT blocks and the IFFT blocksdescribed in this disclosure document may be implemented as configurablesoftware algorithms, where the value of Size N may be modified accordingto the implementation.

Furthermore, although this disclosure is directed to an embodiment thatimplements the Fast Fourier Transform and the Inverse Fast FourierTransform, this is by way of illustration only and should not beconstrued to limit the scope of the disclosure. It may be appreciatedthat in an alternate embodiment of the disclosure, the Fast FourierTransform functions and the Inverse Fast Fourier Transform functions mayeasily be replaced by discrete Fourier transform (DFT) functions andinverse discrete Fourier transform (IDFT) functions, respectively. Itmay be appreciated that for DFT and IDFT functions, the value of the Nvariable may be any integer number (i.e., 1, 4, 3, 4, etc.), while forFFT and IFFT functions, the value of the N variable may be any integernumber that is a power of two (i.e., 1, 2, 4, 8, 16, etc.).

In transmit path circuitry 400, channel coding and modulation block 405receives a set of information bits, applies coding (e.g., LDPC coding)and modulates (e.g., quadrature phase shift keying (QPSK) or quadratureamplitude modulation (QAM)) the input bits to produce a sequence offrequency-domain modulation symbols. Serial-to-parallel block 410converts (i.e., de-multiplexes) the serial modulated symbols to paralleldata to produce N parallel symbol streams where N is the IFFT/FFT sizeused in BS 102 and UE 116. Size N IFFT block 415 then performs an IFFToperation on the N parallel symbol streams to produce time-domain outputsignals. Parallel-to-serial block 420 converts (i.e., multiplexes) theparallel time-domain output symbols from Size N IFFT block 415 toproduce a serial time-domain signal. Add cyclic prefix block 425 theninserts a cyclic prefix to the time-domain signal. Finally, up-converter430 modulates (i.e., up-converts) the output of add cyclic prefix block425 to RF frequency for transmission via a wireless channel. The signalmay also be filtered at baseband before conversion to RF frequency.

The transmitted RF signal arrives at UE 116 after passing through thewireless channel, and reverse operations to those at eNB 102 areperformed. Down-converter 455 down-converts the received signal tobaseband frequency, and remove cyclic prefix block 460 removes thecyclic prefix to produce the serial time-domain baseband signal.Serial-to-parallel block 465 converts the time-domain baseband signal toparallel time-domain signals. Size N FFT block 470 then performs an FFTalgorithm to produce N parallel frequency-domain signals.Parallel-to-serial block 475 converts the parallel frequency-domainsignals to a sequence of modulated data symbols. Channel decoding anddemodulation block 480 demodulates and then decodes the modulatedsymbols to recover the original input data stream.

Each of eNBs 101-103 may implement a transmit path that is analogous totransmitting in the downlink to user equipment 111-116 and may implementa receive path that is analogous to receiving in the uplink from userequipment 111-116. Similarly, each one of user equipment 111-116 mayimplement a transmit path corresponding to the architecture fortransmitting in the uplink to eNBs 101-103 and may implement a receivepath corresponding to the architecture for receiving in the downlinkfrom eNBs 101-103.

Various embodiments of the present disclosure provide for ahigh-performance, scalability with respect to the number and geometry oftransmit antennas, and a flexible CSI feedback (e.g., reporting)framework and structure for LTE enhancements when FD-MIMO with largetwo-dimensional antenna arrays is supported. To achieve highperformance, more accurate CSI in terms MIMO channel is needed at theeNB especially for FDD scenarios. In this case, embodiments of thepresent disclosure recognize that the previous LTE (e.g. Rel. 12)precoding framework (PMI-based feedback) may need to be replaced. Inthis disclosure, properties of FD-MIMO are factored in for the presentdisclosure. For example, the use of closely spaced large 2D antennaarrays that is primarily geared toward high beamforming gain rather thanspatial multiplexing along with relatively small angular spread for eachUE. Therefore, compression or dimensionality reduction of the channelfeedback in accordance with a fixed set of basic functions and vectorsmay be achieved. In another example, updated channel feedback parameters(e.g., the channel angular spreads) may be obtained at low mobilityusing UE-specific higher-layer signaling. In addition, a CSI reporting(feedback) may also be performed cumulatively.

Another embodiment of the present disclosure incorporates a CSIreporting method and procedure with a reduced PMI feedback. This PMIreporting at a lower rate pertains to long-term DL channel statisticsand represents a choice of a group of precoding vectors recommended by aUE to an eNB. The present disclosure also includes a DL transmissionmethod wherein an eNB transmits data to a UE over a plurality ofbeamforming vectors while utilizing an open-loop diversity scheme.Accordingly, the use of long-term precoding ensures that open-looptransmit diversity is applied only across a limited number of ports(rather than all the ports available for FD-MIMO, e.g., 64). This avoidshaving to support excessively high dimension for open-loop transmitdiversity that reduces CSI feedback overhead and improves robustnesswhen CSI measurement quality is questionable.

FIG. 5 illustrates an example structure for a DL subframe 500 accordingto embodiments of the present disclosure. An embodiment of the DLsubframe structure 500 shown in FIG. 1 is for illustration only. Otherembodiments may be used without departing from the scope of the presentdisclosure. The downlink subframe (DL SF) 510 includes two slots 520 anda total of N_(symb) ^(DL) symbols for transmitting of data informationand downlink control information (DCI). The first M_(symb) ^(DL) SFsymbols are used to transmit PDCCHs and other control channels 530 (notshown in FIG. 5 ). The remaining z SF symbols are primarily used totransmit physical downlink shared channels (PDSCHs) 540, 542, 544, 546,and 548 or enhanced physical downlink control channels (EPDCCHs) 550,552, 554, and 556. A transmission bandwidth (BW) comprises frequencyresource units referred to as resource blocks (RBs). Each RB compriseseither N_(sc) ^(RB) subcarriers or resource elements (REs) (such as 12Res). A unit of one RB over one subframe is referred to as a physical RB(PRB). A UE is allocated to M_(PDSCH) RBs for a total ofZ=O_(F)+└(n_(s0)+y·N_(EPDCCH))/D┘ REs for a PDSCH transmission BW. AnEPDCCH transmission is achieved in either one RB or multiple of RBs.

FIG. 6 illustrates an example transmission structure of a physicaluplink shared channel (PUSCH) subframe or a physical uplink controlchannel (PUCCH) subframe 600. Embodiments of the transmission structurefor the PUSCH or the PUCCH over the UL subframe shown in FIG. 6 is forillustration only. Other embodiments could be used without departingfrom the scope of the present disclosure. A UL subframe 610 includes twoslots. Each slot 620 includes N_(symb) ^(UL) symbols 630 fortransmitting data information, uplink control information (UCI),demodulation reference signals (DMRS), or sounding RSs (SRSs). Afrequency resource unit of an UL system BW is a RB. A UE is allocated toN_(RB) RBs 640 for a total of N_(RB)·N_(sc) ^(RB) resource elements(Res) for a transmission BW. For a PUCCH, N_(RB)=1. A last subframesymbol is used to multiplex SRS transmissions 650 from one or more UEs.A number of subframe symbols that are available for data/UCI/DMRStransmission is N_(symb)=2·(N_(symb) ^(UL)−1)−N_(SRS), where N_(SRS)=1if a last subframe symbol is used to transmit SRS and N_(SRS)=0otherwise.

FIG. 7 illustrates an example transmitter block diagram for a physicaldownlink shared channel (PDSCH) subframe 700 according to embodiments ofthe present disclosure. An embodiment of the PDSCH transmitter blockdiagram 700 shown in FIG. 7 is for illustration only. Other embodimentsare used without departing from the scope of the present disclosure.

Information bits 710 are encoded by an encoder 720 (such as a turboencoder) and modulated by a modulator 730, for example using aquadrature phase shift keying (QPSK) modulation. A Serial to Parallel(S/P) converter 740 generates M modulation symbols that are subsequentlyprovided to a mapper 750 to be mapped to REs selected by a transmissionBW selection unit 755 for an assigned PDSCH transmission BW, unit 760applies an inverse fast Fourier transform (IFFT). An output is thenserialized by a parallel to a serial (P/S) converter 770 to create atime domain signal, filtering is applied by a filter 780, and thensignal is transmitted. Additional functionalities, such as datascrambling, a cyclic prefix insertion, a time windowing, aninterleaving, and others are well known in the art and are not shown forbrevity.

FIG. 8 illustrates an example receiver block diagram for a packet datashared channel (PDSCH) subframe 800 according to embodiments of thepresent disclosure. An embodiment of the PDSCH receiver block diagram800 shown in FIG. 8 is for illustration only. One or more of thecomponents illustrated in FIG. 8 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments can beused without departing from the scope of the present disclosure.

A received signal 810 is filtered by a filter 820, and then is output toa resource element (RE) demapping block 830. The RE demapping 830assigns a reception bandwidth (BW) that is selected by a BW selector835. The BW selector 835 is configured to control a transmission BW. Afast Fourier transform (FFT) circuit 840 applies a FFT. The output ofthe FFT circuitry 840 is serialized by a parallel-to-serial converter850. Subsequently, a demodulator 860 coherently demodulates data symbolsby applying a channel estimate obtained from a demodulation referencesignal (DMRS) or a common reference signal (CRS) (not shown), and then adecoder 870 decodes demodulated data to provide an estimate of theinformation data bits 880. The decoder 870 can be configured toimplement any decoding process, such as a turbo decoding process.Additional functionalities such as time-windowing, a cyclic prefixremoval, a de-scrambling, channel estimation, and a de-interleaving arenot shown for brevity.

FIG. 9 illustrates a transmitter block diagram for a physical uplinkshared channel (PUSCH) subframe 900 according to embodiments of thepresent disclosure. One or more of the components illustrated in FIG. 9can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. An embodiment of the PUSCH transmitter block diagram 900shown in FIG. 9 is for illustration only. Other embodiments are usedwithout departing from the scope of the present disclosure.

Information data bits 910 are encoded by an encoder 920 and modulated bya modulator 930. Encoder 920 can be configured to implement any encodingprocess, such as a turbo coding process. A discrete Fourier transform(DFT) circuitry 940 applies a DFT on the modulated data bits. REs aremapped by an RE mapping circuit 950. The REs corresponding to anassigned PUSCH transmission BW are selected by a transmission BWselection unit 955. An inverse FFT (IFFT) circuit 960 applies an IFFT tothe output of the RE mapping circuit 950. After a cyclic prefixinsertion (not shown), filter 970 applies a filtering. The filteredsignal then is transmitted.

FIG. 10 illustrates an example receiver block diagram for a PUSCHsubframe 1000 according to embodiments of the present disclosure. Anembodiment of the PUSCH receiver block diagram 1000 shown in FIG. 10 isfor illustration only. One or more of the components illustrated in FIG.10 can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

A received signal 1010 is filtered by a filter 1020. Subsequently, aftera cyclic prefix is removed (not shown), an FFT circuit 1030 applies anFFT. REs are mapped by an RE mapping circuit 1040. REs 1040corresponding to an assigned PUSCH reception BW are selected by areception BW selector 1045. An inverse DFT (IDFT) circuit 1050 appliesan IDFT. Demodulator 1060 receives an output from IDFT circuit 1050 andcoherently demodulates data symbols by applying a channel estimateobtained from a DMRS (not shown). A decoder 1070 decodes the demodulateddata to provide an estimate of the information data bits 1080. Thedecoder 1070 can be configured to implement any decoding process, suchas a turbo decoding process.

FIG. 11 illustrates an example configuration of a two dimensional (2D)antenna array 1100 which is constructed from 16 dual-polarized antennaelements arranged in a 4×4 rectangular format according to embodimentsof the present disclosure. In this illustration, each labelled antennaelement is logically mapped onto a single antenna port. Two alternativelabelling conventions are depicted for illustrative purposes (such as ahorizontal first in 1110 and a vertical first in 1120). In oneembodiment, one antenna port corresponds to multiple antenna elements(such as physical antennas) combined via a virtualization. This 4×4 dualpolarized array is then viewed as 16×2=32-element array of elements. Thevertical dimension (such as including 4 rows) facilitates an elevationbeamforming in addition to an azimuthal beamforming across a horizontaldimension including 4 columns of dual polarized antennas. A MIMOprecoding in Rel. 12 of the LTE standardization was largely designed tooffer a precoding gain for one-dimensional antenna array. While fixedbeamforming (such as antenna virtualization) is implemented across anelevation dimension, it is unable to reap a potential gain offered by aspatial and frequency selective nature of channels.

In 3GPP LTE specification, MIMO precoding (for beamforming or spatialmultiplexing) can be facilitated via precoding matrix index (PMI)reporting as a component of channel state information (CSI) reporting.The PMI report is derived from one of the following sets of standardizedcodebooks: two antenna ports (single-stage); four antenna ports(single-stage or dual-stage); eight antenna ports (dual-stage);configurable dual-stage eMIMO-Type of ‘CLASS A’ codebook for eight,twelve, or sixteen antenna ports (also known as “nonPrecoded”); andsingle-stage eMIMO-Type of ‘CLASS B’ codebook for two, four, or eightantenna ports (also known as ‘beamformed’).

If an eNodeB follows a PMI recommendation from a UE, the eNB is expectedto precode the eNB's transmitted signal according to a recommendedprecoding vector or matrix for a given subframe and RB. Regardlesswhether the eNB follows this recommendation, the UE is configured toreport a PMI according to a configured precoding codebook. Here a PMI,which may consist of a single index or a pair of indices, is associatedwith a precoding matrix W in an associated codebook.

When dual-stage class A codebook is configured, a resulting precodingmatrix can be described in equation (1). That is, the first stageprecoder can be described as a Kronecker product of a first and a secondprecoding vector (or matrix), which can be associated with a first and asecond dimension, respectively. This type is termed partial KroneckerProduct (partial KP) codebook. The subscripts m and n inW_(m,n)(i_(m,n)) denote precoding stage (first or second stage) anddimension (first or second dimension), respectively. Each of theprecoding matrices W_(m,n) can be described as a function of an indexwhich serves as a PMI component. As a result, the precoding matrix W canbe described as a function of 3 PMI components. The first stage pertainsto a long-term component. Therefore, it is associated with long-termchannel statistics such as the aforementioned angle of departure (AoD)profile and AoD spread. On the other hand, the second stage pertains toa short-term component which performs selection, co-phasing, or anylinear operation to the first component precoderW_(1,1)(i_(1,1))⊗W_(1,2)(i_(1,2)). The precoder W₂(i₂), therefore,performs a linear transformation of the long-term component such as alinear combination of a set of basic functions or vectors associatedwith the column vectors of W_(1,1)(i_(1,1))⊗W_(1,2)(i_(1,2))).

$\begin{matrix}{{W\left( {i_{1,1},i_{1,2},i_{2}} \right)} = \underset{W_{1}({i_{1,1},i_{1,2}})}{\underset{︸}{\begin{matrix}\left( {{W_{1,1}\left( i_{1,1} \right)} \oplus W_{1,2}} \right. & \left. \left( i_{1,2} \right) \right)\end{matrix}}{W_{2}\left( i_{2} \right)}}} & {{Equation}(1)}\end{matrix}$

The above discussion assumes that the serving eNB transmits and a servedUE measures non-precoded CSI-RS (NP CSI-RS). That is, a cell-specificone-to-one mapping between CSI-RS port and TXRU is utilized. Here,different CSI-RS ports have the same wide beam width and direction andhence generally cell wide coverage. This use case can be realized whenthe eNB configures the UE with ‘CLASS A’ eMIMO-Type which corresponds toNP CSI-RS. Other than CQI and RI, CSI reports associated with ‘CLASS A’or ‘nonPrecoded’ eMIMO-Type include a three-component PMI {i_(1,1),i_(1,2), i₂}.

Another type of CSI-RS applicable to FD-MIMO is beamformed CSI-RS (BFCSI-RS). In this case, beamforming operation, either cell-specific (withK>1 CSI-RS resources) or UE-specific (with K=1 CSI-RS resource), isapplied on a non-zero-power (NZP) CSI-RS resource (consisting ofmultiple ports). Here, (at least at a given time/frequency) CSI-RS portshave narrow beam widths and hence not cell wide coverage, and (at leastfrom the eNB perspective) at least some CSI-RS port-resourcecombinations have different beam directions. This beamforming operationis intended to increase CSI-RS coverage.

In addition, when UE-specific beamforming is applied to CSI-RS resource(termed the UE-specific or UE-specifically beamformed CSI-RS); CSI-RSoverhead reduction is possible. UE complexity reduction is also evidentsince the configured number of ports tends to be much smaller than NPCSI-RS counterpart of the UE. When a UE is configured to receive BFCSI-RS from a serving eNB, the UE can be configured to report PMIparameter(s) associated with a second-stage precoder without theassociated first-stage precoder or, in general, associated with asingle-stage precoder/codebook. This use case can be realized when theeNB configures the UE with ‘CLASS B’ eMIMO-Type which corresponds to BFCSI-RS. Other than CQI and RI, CSI reports associated with ‘CLASS B’ or‘beamformed’ eMIMO-Type (with one CSI-RS resource and alternativecodebook) include a one-component PMIn. Although a single PMI definedwith respect to a distinct codebook, this PMI can be associated with thesecond-stage PMI component of ‘CLASS A’/‘nonPrecoded’ codebooks i₂.

Therefore, given a precoding codebook (a set of precoding matrices), aUE measures a CSI-RS in a subframe designated to carry CSI-RS,calculates/determines a CSI (including PMI, RI, and CQI where each ofthese three CSI parameters can consist of multiple components) based onthe measurement, and reports the calculated CSI to a serving eNB. Inparticular, this PMI is an index of a recommended precoding matrix inthe precoding codebook. Similar to that for the first type, differentprecoding codebooks can be used for different values of RI. The measuredCSI-RS can be one of the two types: non-precoded (NP) CSI-RS andbeamformed (BF) CSI-RS. As mentioned, in Rel. 13, the support of thesetwo types of CSI-RS is given in terms of two eMIMO-Types: ‘CLASS A’(with one CSI-RS resource) and ‘CLASS B’ (with one or a plurality ofCSI-RS resources), respectively.

In scenarios where DL long-term channel statistics can be measuredthrough UL signals at a serving eNB, UE-specific BF CSI-RS can bereadily used. This is typically feasible when UL-DL duplex distance issufficiently small. When this condition does not hold, however, some UEfeedback is necessary for the eNB to obtain an estimate of DL long-termchannel statistics (or any of representation thereof). To facilitatesuch a procedure, a first BF CSI-RS transmitted with periodicity T1(milliseconds or ms) and a second NP CSI-RS transmitted with periodicityT2 (ms), where T1≤T2. This approach is termed hybrid CSI-RS. Theimplementation of hybrid CSI-RS is largely dependent on the definitionof CSI process and NZP CSI-RS resource.

In LTE specification, the aforementioned precoding codebooks areutilized for CSI reporting. Two schemes of CSI reporting modes aresupported (e.g., PUSCH-based aperiodic CSI (A-CSI) and PUCCH-basedperiodic CSI (P-CSI)). In each scheme, different modes are defined basedon frequency selectivity of CQI and/or PMI, that is, whether wideband orsubband reporting is performed. The supported CSI reporting modes aregiven in Table 1.

TABLE 1 CQI and PMI Feedback Types for PUSCH CSI reporting Modes PMIFeedback Type No Single Multiple PMI PMI PMI PUSCH CQI Wideband Mode 1-2(wideband CQI) Feedback Type UE Selected Mode 2-0 Mode 2-2 (subband CQI)Higher Layer- Mode 3-0 Mode 3-1 Mode 3-2 configured (subband CQI)

TABLE 2 CQI and PMI Feedback Types for PUCCH CSI reporting Modes PMIFeedback Type No Single PMI PMI PUCCH CQI Wideband Mode 1-0 Mode 1-1Type (wideband CQI) Feedback UE Selected Mode 2-0 Mode 2-1 (subband CQI)

According to the [REF6], the hybrid CSI reporting based on non-precodedand beam-formed CSI-RS associated with two eMIMO-Types is supported inLTE specification.

In the following, for brevity, FDD is considered as the duplex methodfor both DL and UL signaling but the embodiments of the presentdisclosure are also directly applicable to TDD. Terms such as‘non-precoded’ (or ‘NP’) CSI-RS and ‘beamformed’ (or ‘BF’) CSI-RS areused throughout this present disclosure. The essence of this presentdisclosure does not change when different terms or names are used torefer to these two CSI-RS types. The same holds for CSI-RS resource.CSI-RS resources associated with these two types of CSI-RS can bereferred to as ‘a first CSI-RS resource’ and ‘a second CSI-RS resource’,or ‘CSI-RS-A resource’ and ‘CSI-RS-B resource’. Subsequently, the labels‘NP’ and ‘BF’ (or ‘np’ and ‘bf’) are exemplary and can be substitutedwith other labels such as ‘1’ and ‘2’, ‘A’ or ‘B’. Alternatively,instead of using categories such as CSI-RS type or CSI-RS resource type,a category of CSI reporting class can also be used. For instance, NPCSI-RS is associated with eMIMO-Type of ‘CLASS A’ while UE-specific BFCSI-RS is associated with eMIMO-Type of ‘CLASS B’ with one CSI-RSresource.

Throughout this present disclosure, 2D dual-polarized array is usedsolely for illustrative purposes, unless stated otherwise. Extensions to2D single-polarized array are straightforward for those skilled in theart.

FIG. 12 illustrates an example dual-polarized antenna port layouts for{2, 4, 8, 12, 16} ports 1200 according to embodiments of the presentdisclosure. An embodiment of the dual-polarized antenna port layouts for{2, 4, 8, 12, 16} ports 1200 shown in FIG. 12 is for illustration only.One or more of the components illustrated in FIG. 12 can be implementedin specialized circuitry configured to perform the noted functions orone or more of the components can be implemented by one or moreprocessors executing instructions to perform the noted functions. Otherembodiments are used without departing from the scope of the presentdisclosure.

As shown in FIG. 12 , 2D antenna arrays are constructed from N₁×N₂dual-polarized antenna elements arranged in a (N₁, N₂) rectangularformat for 2, 4, 8, 12, 16 antenna ports. In FIG. 12 , each antennaelement is logically mapped onto a single antenna port. In general, oneantenna port may correspond to multiple antenna elements (physicalantennas) combined via a virtualization. This N₁×N₂ dual polarized arraycan then be viewed as 2N₁N₂-element array of elements.

The first dimension consists of N₁ columns and facilitates azimuthbeamforming. The second dimension similarly consists of N₂ rows andallows elevation beamforming. MIMO precoding in LTE specification waslargely designed to offer precoding (beamforming) gain forone-dimensional (1D) antenna array using 2, 4, 8 antenna ports, whichcorrespond to (N₁, N₂) belonging to {(1, 1), (2, 1), (4, 1)}. Whilefixed beamforming (i.e. antenna virtualization) can be implementedacross the elevation dimension, it is unable to reap the potential gainoffered by the spatial and frequency selective nature of the channel.Therefore, MIMO precoding in LTE specification is designed to offerprecoding gain for two-dimensional (2D) antenna array using 8, 12, 16antenna ports, which correspond to (N₁, N₂) belonging to {(2, 2), (2,3), (3, 2), (8, 1), (4, 2), (2, 4)}.

Although (N₁, N₂)=(6, 1) case has not been supported in LTEspecification, it may be supported in future releases. The embodimentsof the present disclosure are general and are applicable to any (N₁, N₂)values including (N₁, N₂)=(6, 1). The first and second dimensions asshown in FIG. 12 are for illustration only. The present disclosure isapplicable to the case, in which the first and second dimensions areswapped, i.e., first and second dimensions respectively correspond toelevation and azimuth or any other pair of directions.

FIG. 13 illustrates example dual-polarized antenna port layouts 1300 for{20, 24, 28, 32} ports according to embodiments of the presentdisclosure. An embodiment of the dual-polarized antenna port layouts1300 shown in FIG. 13 is for illustration only. One or more of thecomponents illustrated in FIG. 13 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

For 8 antenna ports {15, 16, 17, 18, 19, 20, 21, 22}, 12 antenna ports{15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26}, 16 antenna ports {15,16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30}, and UEconfigured with higher layer parameter eMIMO-Type, and eMIMO-Type is setto ‘CLASS A’, each PMI value corresponds to three codebook indices givenin Table 4, where the quantities φ_(n), u_(m) and v_(l,m) are given byequation (2):

$\begin{matrix}{\varphi_{n} = e^{j\pi n/2}} & {{Equation}(2)}\end{matrix}$ $u_{m} = \left\lbrack \begin{matrix}1 & e^{j\frac{2\pi m}{O_{2}N_{2}}} & \ldots & \left. e^{j\frac{2\pi{m({N_{2} - 1})}}{O_{2}N_{2}}} \right\rbrack\end{matrix} \right.$ $v_{l,m} = \left\lbrack \begin{matrix}u_{m} & {e^{j\frac{2\pi l}{O_{1}N_{1}}}u_{m}} & \ldots & \left. {e^{j\frac{2\pi{l({N_{1} - 1})}}{O_{1}N_{1}}}u_{m}} \right\rbrack^{T}\end{matrix} \right.$

In equation (2), the values of N₁, N₂, O₁, and O₂ are configured withthe higher-layer parameters codebook-Config-N1, codebook-Config-N2,codebook-Over-Sampling-RateConfig-O1, andcodebook-Over-Sampling-RateConfig-O2, respectively. The supportedconfigurations of (O₁, O₂) and (N₁, N₂) for a given number of CSI-RSports are given in Table 3. The number of CSI-RS ports, P, is 2N₁N₂.

A UE is not expected to be configured with value of Codebook-Config setto 2 or 3, if the value of codebook-Config-N2 is set to 1. A UE may onlyuse i_(1,2)=0 and shall not report i_(1,2) if the value ofcodebook-Config-N2 is set to 1. A first PMI value i₁ corresponds to thecodebook indices pair {i_(1,1), i_(1,2)}, and a second PMI value i₂corresponds to the codebook index i₂ given in Table 4.

In some embodiments, a codebook subsampling is supported. Thesub-sampled codebook for PUCCH mode 2-1 for value of parameterCodebook-Config set to 2, 3, or 4 is defined in LTE specification forPUCCH Reporting Type 1a.

TABLE 3 Supported configurations of (O₁,O₂) and (N₁,N₂) Number of CSI-RSantenna ports, P (N₁,N₂) (O₁,O₂)  8 (2,2) (4,4), (8,8) 12 (2,3) (8,4),(8,8) (3,2) (8,4), (4,4) 16 (2,4) (8,4), (8,8) (4,2) (8,4), (4,4) (8,1)(4,—), (8,—)

TABLE 4 Codebook for 1-layer CSI reporting using antenna ports 15 to14 + P Value of Codebook- i₂ Config i_(1,1) i_(1,2) 1 0, 1, . . . , O₁N₁− 1 0, 1, . . . , O₂N₂ − 1 W_(i) _(1,1) _(,i) _(1,2) _(,0) ⁽¹⁾ W_(i)_(1,1) _(,i) _(1,2) _(,1) ⁽¹⁾ W_(i) _(1,1) _(,i) _(1,2) _(,2) ⁽¹⁾ W_(i)_(1,1) _(,i) _(1,2) _(,3) ⁽¹⁾ where$W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{l,m} \\{\varphi_{n}v_{l,m}}\end{bmatrix}}$ Value of Codebook- i₂ Config i_(1,1) i_(1,2) 0 1 2 3 2${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2i) _(1,1) _(,2i) _(1,2)_(,0) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,1) ⁽¹⁾ W_(2i) _(1,1) _(,2i)_(1,2) _(,2) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(,3) ⁽¹⁾ Value ofCodebook- i₂ Config i_(1,1) i_(1,2) 4 5 6 7 2${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2i) _(1,1) _(+1,2i) _(1,2)_(,0) ⁽¹⁾ W_(2i) _(1,1) _(+1,2i) _(1,2) _(,1) ⁽¹⁾ W_(2i) _(1,1) _(+1,2i)_(1,2) _(,2) ⁽¹⁾ W_(2i) _(1,1) _(+1,2i) _(1,2) _(,3) ⁽¹⁾ Value ofCodebook- i₂ Config i_(1,1) i_(1,2) 8 9 10 11 2${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2i) _(1,1) _(,2i) _(1,2)_(+1,0) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(+1,1) ⁽¹⁾ W_(2i) _(1,1) _(,2i)_(1,2) _(+1,2) ⁽¹⁾ W_(2i) _(1,1) _(,2i) _(1,2) _(+1,3) ⁽¹⁾ Value ofCodebook- i₂ Config i_(1,1) i_(1,2) 12 13 14 15 2${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2i) _(1,1) _(+1,2i) _(1,2)_(+1,0) ⁽¹⁾ W_(2i) _(1,1) _(+1,2i) _(1,2) _(+1,1) ⁽¹⁾ W_(2i) _(1,1)_(+1,2i) _(1,2) _(+1,2) ⁽¹⁾ W_(2i) _(1,1) _(+1,2i) _(1,2) _(+1,3) ⁽¹⁾where $W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{l,m} \\{\varphi_{n}v_{l,m}}\end{bmatrix}}$ Value of Codebook- i₂ Config i_(1,1) i_(1,2) 0 1 2 3 3${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2x,2y,0) ⁽¹⁾ W_(2x,2y,1) ⁽¹⁾W_(2x,2y,2) ⁽¹⁾ W_(2x,2y,3) ⁽¹⁾ Value of Codebook- i₂ Config i_(1,1)i_(1,2) 4 5 6 7 3 ${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2x+2,2y,0) ⁽¹⁾ W_(2x+2,2y,1)⁽¹⁾ W_(2x+2,2y,2) ⁽¹⁾ W_(2x+2,2y,3) ⁽¹⁾ Value of Codebook- i₂ Configi_(1,1) i_(1,2) 8 9 10 11 3 ${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2x+1,2y+1,0) ⁽¹⁾W_(2x+1,2y+1,1) ⁽¹⁾ W_(2x+1,2y+1,2) ⁽¹⁾ W_(2x+1,2y+1,3) ⁽¹⁾ Value ofCodebook- i₂ Config i_(1,1) i_(1,2) 12 13 14 15 3${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2x+3,2y+1,0) ⁽¹⁾W_(2x+3,2y+1,1) ⁽¹⁾ W_(2x+3,2y+1,2) ⁽¹⁾ W_(2x+3,2y+1,3) ⁽¹⁾ where x =i_(1,1), y = i_(1,2),${W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{l,m} \\{\varphi_{n}v_{l,m}}\end{bmatrix}}},$ if N₁ ≥ N₂ x = i_(1,2), y = i_(1,1),${W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{m,l} \\{\varphi_{n}v_{m,l}}\end{bmatrix}}},$ if N₁ ≥ N₂ Value of Codebook- i₂ Config i_(1,1)i_(1,2) 0 1 2 3 4 ${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2x,2y,0) ⁽¹⁾ W_(2x,2y,1) ⁽¹⁾W_(2x,2y,2) ⁽¹⁾ W_(2x,2y,3) ⁽¹⁾ Value of Codebook- i₂ Config i_(1,1)i_(1,2) 4 5 6 7 4 ${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2x+1,2y,0) ⁽¹⁾ W_(2x+1,2y,1)⁽¹⁾ W_(2x+1,2y,2) ⁽¹⁾ W_(2x+1,2y,3) ⁽¹⁾ Value of Codebook- i₂ Configi_(1,1) i_(1,2) 8 9 10 11 4 ${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2x+2,2y,0) ⁽¹⁾ W_(2x+2,2y,1)⁽¹⁾ W_(2x+2,2y,2) ⁽¹⁾ W_(2x+2,2y,3) ⁽¹⁾ Value of Codebook- i₂ Configi_(1,1) i_(1,2) 12 13 14 15 4 ${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$ W_(2x+3,2y,0) ⁽¹⁾ W_(2x+3,2y,1)⁽¹⁾ W_(2x+3,2y,2) ⁽¹⁾ W_(2x+3,2y,3) ⁽¹⁾ where x = i_(1,1), y = i_(1,2),${W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{l,m} \\{\varphi_{n}v_{l,m}}\end{bmatrix}}},$ if N₁ ≥ N₂ x = i_(1,2), y = i_(1,1),${W_{l,m,n}^{(1)} = {\frac{1}{\sqrt{P}}\begin{bmatrix}v_{m,l} \\{\varphi_{n}v_{m,l}}\end{bmatrix}}},$ if N₁ ≥ N₂

The mapping between Codebook-Config parameter to rank 1 beam groupingindicated by (i_(1,1), i_(1,2)) is illustrated in FIG. 29 . As shown,Codebook-Config=1 corresponds to one beam (black square located at (0,0)), and Codebook-Config=2, 3, 4 correspond to 4 beams (shown as blacksquares) which are located inside the (4, 2) beam grid depending on theCodebook-Config value.

Note that Rel. 10 8-Tx and Rel. 12 4-Tx codebooks can be mapped toCodebook-Config 4 because the codebooks correspond to 1D antenna portlayouts.

LTE supports {20, 24, 28, 32} antenna ports in Rel. 14. Assumingrectangular (1D or 2D) port layouts, there are several possible (N₁, N₂)values for {20, 24, 28, 32} ports. An illustration of 1D and 2D antennaport layouts for these (N₁, N₂) values are shown in FIG. 13 .

FIG. 14 illustrates example explicit channel state information (CSI)feedback framework 1400 according to embodiments of the presentdisclosure. An embodiment of the explicit CSI feedback framework 1400shown in FIG. 14 is for illustration only. One or more of the componentsillustrated in FIG. 14 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments: let N_(r) be the number of receive antennas at theUE; let H^((f,r,p)) be the channel associated with the f-th SB, r-threceive antenna at the UE, and p-th polarization. Note that H^((f,r,p))is a column vector of size N₁N₂×1; Let H^((f,r)) be the channelassociated with the f-th SB, r-th receive antenna at the UE, and bothpolarizations (+45 and −45). Note that H^((f,r)) is a column vector ofsize 2N₁N₂×1; Let H^((f,p)) be the channel associated with the f-th SB,all N_(r) receive antennas at the UE, and p-th polarization. Note thatH^((f,p)) is a matrix of size N₁N₂×N_(r); Let H^((f)) be the channelassociated with the f-th SB, all N_(r) receive antennas at the UE, andboth polarizations (+45 and −45). Note that H^((f)) is a matrix of size2N₁N₂×N_(r).

For brevity, in the rest of present disclosure, we will use the notationH^((I)), where (I) belongs to {(f, r, p), (f, r), (f, p), (f)} torepresent one of above four types of channel notations unless mentionedotherwise. In case of SB comprising of multiple subcarriers, we will useH_(k) ^((I)) to denote the channel for subcarrier k in SB f.

In some embodiments, as shown in FIG. 14 , a UE is configured with a‘Class E’ or ‘Class Explicit’ eMIMO-Type in which DL channel H^((I)) orone of derivatives (Alt 0-Alt 4 below) is reported based on the LCframework as Σ_(l=0) ^(L-1)c_(l)b_(l) using a double codebook forexplicit feedback: W=W₁W₂, where: W₁ is for WB and long-term basisvectors {b_(l): l=0, 1, . . . , L−1} feedback; W₂ is for SB andshort-term LC coefficients {c_(l): l=0, 1, . . . , L−1} feedback; and Lis the size of the basis vector set.

This configuration is via RRC signaling for example. This eMIMO-Type canbe associated with NP or BF CSI-RS with K≥1 resources. The alternativesfor DL channel and the DL channel's derivatives and their LCrepresentations are determined.

In one embodiment of Alt 0-0, for at least one subcarrier k in SB f, thechannel is represented as H_(k) ^((I))≈Σ_(l=0) ^(L-1)c_(l)b_(l), wherethe dimension of b_(l) is the same as H_(k) ^((I)) depending on I.

In another embodiment of Alt 0-1, for at least one subcarrier k in SB f,the channel is represented as H_(k) ^((I))≈Σ_(l=0)^(L-1)c_(l)b_(T,l)b_(R,l) ^(H), where b_(T,l) is a column vector oflength N₁N₂ or 2N₁N₂ depending on I and b_(R,l) is a column vector oflength N_(r). Note that the l-th basis vector is decomposed into the Txand Rx basis vector pair (b_(T,l), b_(R,l)).

In yet another embodiment of Alt 1: Left (Tx) covariance matrix, for SBf, the left (Tx) covariance matrix of H^((I)) is represented as

$E_{T} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{k}^{(I)} \right)\left( H_{k}^{(I)} \right)^{H}} \right)}} \approx {\sum_{l = 0}^{L_{T} - 1}{c_{T,l}b_{T,l}b_{T,l}^{H}}}}$

where b_(T,l) is defined in Alt 0-1, c_(T,l) is the l-th Tx coefficient,and L_(T) is the number of Tx basis vectors.

In yet another embodiments of Alt 2: Left and right (Tx and Rx)covariance matrices, for SB f, the left and right (Tx and Rx) covariancematrices of H^((I)) where (I) belongs to {(f, p), (f)} are representedas E_(T) same as in Alt 1 and

${E_{R} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{k}^{(I)} \right)^{H}\left( H_{k}^{(I)} \right)} \right)}} \approx {\sum_{l = 0}^{L_{R} - 1}{c_{R,l}b_{R,l}b_{R,l}^{H}}}}},$

where b_(R,l) is defined in Alt 0-1, c_(R,l) is the l-th Rx coefficient,and L_(R) is the number of Rx basis vectors.

In yet another embodiment of Alt 3: Left (Tx) dominant eigenvector, forSB f, the left (Tx) dominant eigenvector of H^((I)) which is derivedusing Eigen decomposition of Tx covariance matrix E_(T) is representedas e_(T,1)≈Σ_(l=0) ^(L) ^(T) ⁻¹c_(T,l)b_(T,l).

In yet another embodiment of Alt 4: Left and right (Tx and Rx) dominanteigenvectors, for SB f, the left and right (Tx and Rx) dominanteigenvectors of H^((I)) which are derived using Eigen decomposition ofTx and Rx covariance matrix E_(T) and E_(R), respectively, and where (I)belongs to {(f, p), (f)}. In one example of Alt 4-0: separate, e_(T,l)same as in Alt 3 and e_(R,1)≈Σ_(l=0) ^(L) ^(R) ⁻¹c_(R,l)b_(R,l). Inanother example of Alt 4-1: joint, e_(T,1)e_(R,1) ^(H)≈Σ_(l=0)^(L-1)c_(l)b_(T,l)b_(R,l) ^(H). In Alt 3 and 4, the most dominanteigenvectors are considered. The alternatives, however, can be extendedto multiple eigenvectors.

Note that in Alt 1-Alt 3 and Alt 4-0, the master basis set (W₁)comprises of two separate master basis sets, one for each of Tx and Rxbasis vectors {b_(T,l)}_(l=0) ^(L) ^(T) ⁻¹ and {b_(R,l)}_(l=0) ^(L) ^(R)⁻¹. The number of Tx and Rx basis vectors can be the same (i.e.,L_(T)=L_(R)) or the number of Tx and Rx basis vector can be different(i.e., L_(T)≠L_(R)). In Alt 0 and Alt 4-1, the master basis set (W₁) isa joint set of L basis vectors {b_(l)}_(l=0) ^(L-1) or {(b_(T,l),b_(R,l))}_(l=0) ^(L-1).

In some embodiments, the master basis sets for joint basis vector{b_(l)}_(l=0) ^(L-1) (Alt 0-0) and {(b_(T,l), b_(R,l))}_(l=0) ^(L-1)(Alt 0-1 and Alt 4-1), or separate Tx and Rx basis vectors{b_(T,l)}_(l=0) ^(L) ^(T) ⁻¹ and {b_(R,l)}_(l=0) ^(L) ^(R) ⁻¹ may be thesame for all alternatives Alt 0-Alt 4. In some embodiments, the masterbasis sets can be specific to an alternative. Similarly, in one method,the codebook for joint LC coefficients {c_(l)}_(l=0) ^(L-1) or separateTx and Rx LC coefficients {c_(T,l)}_(l=0) ^(L) ^(T) ⁻¹ and{c_(R,l)}_(l=0) ^(L) ^(R) ⁻¹ may be the same for all alternatives Alt0-Alt 4. In another method, the separate Tx and Rx LC coefficients canbe specific to an alternative.

In some embodiments, the UE is also configured with one or both of I andone alternative from Alt 0-Alt 4 via RRC signaling. In some embodiments,the UE reports preferred values for them. For example, this reportingcan be a part of the explicit CSI report. In some embodiments, thereporting is fixed, for example I=(f, r) and Alt 0.

In some embodiments, the bases {b_(l)}_(l=0) ^(L-1) to represent DLchannels at multiple Rx antennas (in case of H^((f)) and H^((f,p))) arethe same, and hence only one basis set is reported. In some embodiments,bases {b_(l)}_(l=0) ^(L-1) are different, and hence a basis set isreported for each Rx antenna. Similarly, in one embodiment, the bases{b_(l)}_(l=0) ^(L-1) to represent DL channels at two polarizations (incase of H^((f)) and H^((f,r))) are the same, and hence only one basisset is reported. In another embodiment, the bases {b_(l)}_(l=0) ^(L-1)are different, and hence a basis set is reported for each polarization.

Similarly, in one embodiment, the bases {b_(l)}_(l=0) ^(L-1) torepresent multiple eigenvectors are the same, and hence only one basisset is reported for all reported eigenvectors. In another embodiment,the bases {b_(l)}_(l=0) ^(L-1) are different, and hence a basis set isreported for each reported eigenvector.

In some embodiments, in addition to channel or one of derivatives, theexplicit CSI report can also include one of the following: (1) at leastone CQI representing either, wherein quantized largest eigenvalueassociated with the dominant Tx and Rx eigenvectors or SNR; (2) RI toindicate a preferred rank; or (3) both CQI and RI, where reported CQImay or may not correspond to reported RI. For instance, only one CQI isreported but the reported RI>1.

In some embodiments, RI is not fed back in the explicit CSI report. Insuch embodiments, the explicit CSI feedback may correspond to apre-determined or fixed RI. For example: RI=1. In this example, the UEreports the dominant Tx eigenvector (associated with the largesteigenvalue) or both Tx and Rx dominant eigenvectors as explicit CSIfeedback; and RI=maximum possible rank, i.e. RI=max(2N₁N₂, N_(r)). Inthis example, the UE reports either the full DL channel or alleigenvectors or covariance matrix.

In some embodiments, the RI is configured to the UE via higher-layer RRCsignaling. The UE reports the explicit CSI feedback based on theconfigured RI.

In some embodiments, RI is fed back in the explicit CSI report. In thecase of channel and covariance matrix feedback, the reported RIcorresponds to a preferred rank, and in the case of eigenvectorfeedback, the reported RI corresponds to the number of reported dominanteigenvectors associated with largest eigenvalues.

In some embodiments, a UE is configured with Rel. 13 (or extended tofuture releases such as Rel. 14) Class A W₁ codebook as the W₁ codebookor master basis set for the proposed LC based ‘Class A-E’ or ‘ClassA-Explicit’ eMIMO-Type. This configuration can be signaled in the sameway as in Rel. 13, i.e., via RRC signaling of five parameters N₁, N₂,O₁, O₂, and Codebook-Config. An example of rank 1-2 Class A W₁ codebookis shown in Table 7, where the group of beams indicated by (i_(1,1),i_(1,2)) is expressed as w_(i) _(1,1) _(,i) _(1,2) , where thequantities u_(m) and v_(l,m) are given by:

$u_{m} = \left\lbrack \begin{matrix}1 & e^{j\frac{2\pi m}{O_{2}N_{2}}} & \ldots & \left. e^{j\frac{2\pi{m({N_{2} - 1})}}{O_{2}N_{2}}} \right\rbrack\end{matrix} \right.$ $v_{l,m} = \left\lbrack \begin{matrix}u_{m} & {e^{j\frac{2\pi l}{O_{1}N_{1}}}u_{m}} & \ldots & \left. {e^{j\frac{2\pi{l({N_{1} - 1})}}{O_{1}N_{1}}}u_{m}} \right\rbrack^{T}\end{matrix} \right.$

where the values of N₁, N₂, O₁, and O₂ are configured with thehigher-layer parameters codebook-Config-N1, codebook-Config-N2,codebook-Over-Sampling-RateConfig-O1, andcodebook-Over-Sampling-RateConfig-O2, respectively.

The supported configurations of (O₁, O₂) and (N₁, N₂) for a given numberof CSI-RS ports in the Class A eMIMO-Type are given in Table 3. For 20,24, 28, and 32 CSI-RS ports, the supported configurations of (O₁, O₂)and (N₁, N₂) can be added to the table. The number of CSI-RS ports, P,is 2N₁N₂.

A UE is not expected to be configured with value of Codebook-Config setto 2 or 3, if the value of codebook-Config-N2 is set to 1. A UE may onlyuse i_(1,2)=0 and shall not report i_(1,2) if the value ofcodebook-Config-N2 is set to 1.

TABLE 6 Supported configurations of (O₁,O₂) and (N₁,N₂) Number of CSI-RSantenna ports, P (N₁,N₂) (O₁,O₂)  8 (2,2) (4,4), (8,8) 12 (2,3) (8,4),(8,8) (3,2) (8,4), (4,4) 16 (2,4) (8,4), (8,8) (4,2) (8,4), (4,4) (8,1)(4,—), (8,—) 20 24 28 32

TABLE 7 W₁ Codebook for 1-layer and 2-layer CSI reporting using antennaports 15 to 14 + P Value of Codebook- Config i_(1,1) i_(1,2) w_(i)_(1,1) _(,i) _(1,2) 1 0, 1, . . . , N₁O₁ − 1 0, 1, . . . , N₂O₂ − 1$W_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}v_{i_{1,1},i_{1,2}}}$2 ${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$$w_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}v_{{{2i_{1,1}} + 1},{2i_{1,2}}}v_{{2i_{1,1}},{2i_{1,1}},{{2i_{1,2}} + 1}}v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}}} \right\rbrack}$3 ${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$${w_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}v_{{{2i_{1,1}} + 2},{2i_{1,2}}}v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}}v_{{{2i_{1,1}} + 3},{{2i_{1,2}} + 1}}} \right\rbrack}},$  if N₁ ≥ N₂${w_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}v_{{2i_{1,1}},{{2i_{1,2}} + 2}}v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 1}}v_{{{2i_{1,1}} + 1},{{2i_{1,2}} + 3}}} \right\rbrack}},$  if N₁ < N₂ 4 ${0,1,\ldots,\frac{N_{1}O_{1}}{2}} - 1$${0,1,\ldots,\frac{N_{2}O_{2}}{2}} - 1$${w_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}v_{{{2i_{1,1}} + 1},{2i_{1,2}}}v_{{{2i_{1,1}} + 2},{2i_{1,2}}}v_{{{2i_{1,1}} + 3},{2i_{1,2}}}} \right\rbrack}},$  if N₁ ≥ N₂${w_{i_{1,1},i_{1,2}} = {\frac{1}{\sqrt{N_{1}N_{2}}}\left\lbrack {v_{{2i_{1,1}},{2i_{1,2}}}v_{{2i_{1,1}},{{2i_{1,2}} + 1}}v_{{2i_{1,1}} + {2i_{1,2}} + 2}v_{{2i_{1,1}} + {2i_{1,2}} + 3}} \right\rbrack}},$  if N₁ < N₂

In some embodiments, the mapping of Codebook-Config to DFT beam groupremains the same as in Rel. 13 Class A codebook or Rel. 13 Class Acodebook's extensions (see FIG. 29 ). In this case, the configured valuefor Codebook-Config can be restricted to 2, 3, and 4 in order to havemultiple beams (L=4) for LC.

In some embodiments, 20, 24, 28, 32 CSI-RS ports, if Codebook-Config=1,then the UE is configured with implicit CSI feedback as in Rel. 13 or inRel. 14, and if Codebook-Config=2, 3, 4, then the UE is configured withadvanced CSI feedback such as explicit CSI feedback proposed in thepresent disclosure.

In some embodiments, Codebook-Config=1 case is mapped to a new beamgroup of L=4 beams either in 1D or 2D). For example, it can be mapped toCodebook-Config=4. Then, all possible values of Codebook-Config can beconfigured.

According to the configuration, the UE derives and reports the first PMIi₁ or (i_(1,1), i_(1,2)) indicating L=4 DFT beams, b₀, b₁, b₂, b₃ asbasis vectors. This reporting can be periodic using PUCCH CSI reportingmodes. Or, the reporting can be aperiodic using PUSCH CSI reportingmodes.

In some embodiment 1, if (I)=(f, r), then both polarizations (+45 and−45) are included in H^((I)). So, the UE reports a co-phase value ϕ_(l)for each basis vector b_(l) using the coefficient codebook C_(co-ph). Inthis case, the l-th basis vector is given by

$\begin{bmatrix}b_{l} \\{\phi_{l}b_{l}}\end{bmatrix}.$

Two examples for C_(co-ph) are as follows: (1) C_(co-ph)={1,j,−1,−j}.So, 2L bits are needed to indicate {ϕ_(l): l=0, 1, . . . , L−1}. Theindication can be WB or SB; and C_(co-ph)=C_(co-ph,1)C_(co-ph,2) where

$C_{{{co} - {ph}},1} = \left\{ {e^{j\frac{\pi}{4}},e^{j\frac{3\pi}{4}},e^{j\frac{5\pi}{4}},e^{j\frac{7\pi}{4}}} \right\}$

is for WB component and

$C_{{{co} - {ph}},2} = \left\{ {e^{j\frac{\pi}{4}},e^{- j\frac{\pi}{4}}} \right\}$

is for SB component. So, 2L bits WB and L bits per SB indication areneeded in this case.

In some embodiments 2, if (I)=(f, p), then all receive antennas at theUE are included in H^((I)). So, in addition to Tx basis vector b_(T,l)indicated by the first PMI i₁ or (i_(1,1), i_(1,2)), the UE also reportsRx basis vectors b_(R,l). This indication can either be: joint asb_(l)=(b_(T,l), b_(R,l)) using the first PMI i₁ or (i_(1,1), i_(1,2));or separate as b_(T,l) and b_(R,l) using the first PMI i₁ or (i_(1,1),i_(1,2)) for b_(T,l) and another WB and long-term reporting for b_(R,l),where reporting of Tx and Rx basis vectors can be in the same ordifferent PMI reporting instances (or subframes).

In some embodiments, two examples of the master Rx basis set are asfollows: fixed/configured: b_(R,l) are fixed or eNB configures them, andhence no indication is needed; and DFT codebook based: each b_(R,l) is aDFT beam (1D or 2D) from a DFT codebook with an integer oversamplingfactor ≥1.

Two examples of the DFT based codebook are as follows: single DFTcodebook such as legacy {1, 2, 4}-Tx codebooks; and double DFT codebooksuch as legacy {4, 8, 12, 16}-Tx double codebooks.

In some embodiment 3, if (I)=(f), then the UE reports Tx and Rx basisvectors, b_(T,l) and b_(R,l), and co-phase values ϕ_(l) for all Tx basisvectors by combining the aforementioned embodiments 1 and 2.

In some embodiments, a UE is configured with an extended Class A W₁codebook as the W₁ codebook or master basis set for the proposed LCbased ‘Class E’ or ‘Class Explicit’ eMIMO-Type in which more beams areincluded in W₁ codebook. For example, the number of beams L=8 and newCodebook-Config=5, 6, . . . are used to configure these extended beamgroups. A few examples of extended beam groups are shown in FIG. 30 .

In some embodiments, a UE is configured with multiple Codebook-Configvalues or beam groups via RRC signaling, and the UE reports a preferredCodebook-Config value or beam group in the UE's explicit CSI report. Theconfigured Codebook-Config values may or may not correspond to the samenumber of beams.

In some embodiments, a UE is configured with an additional Class A W₁codebook parameter (p₁, p₂) pairs via RRC signaling, which respectivelyare beam spacing parameters in 1st and 2nd dimensions. The configuredClass A W₁ codebook is used as the W₁ codebook or master basis set forthe proposed LC based ‘Class E’ or ‘Class Explicit’ eMIMO-Type accordingto some embodiments of this present disclosure. The beam spacingparameter determines the spacing between the two adjacent beams in abeam group (indicated by i₁ or (i_(1,1), i_(1,2)) of W1 codebook). Fordimension d=1, 2, starting from the beam index i_(1,d), indices of L_(d)beams forming a beam group are i_(1,d), i_(1,d)+p_(d), i_(1,d)+2p_(d), .. . , i_(1,d)+(L_(d)−1)p_(d). Example values of beam spacing parametersinclude p₁ in {1, . . . , O₁/2, O₁} and p₂ in {1, . . . , O₂/2, O₂}.Note that p₁=O₁ implies orthogonal beams in 1st dimension.

In some embodiments, the UE is configured with orthogonal DFT beams asthe basis set for the LC based explicit CSI feedback. In one example,for 1D port layouts, L (=L₁)=N₁ orthogonal DFT beams form the basis set.The master basis set in this case corresponds to the 1D DFT codebook oflength N₁ and with an oversampling factor O₁. In another example, for 2Dport layouts, L (=L₁×L₂)=N₁×N₂ (2D) orthogonal DFT beams form the basisset. The master basis set in this case corresponds to the 2D DFTcodebook, which can be obtained by the Kronecker product of two 1D DFTcodebooks of lengths N₁ and N₂ and with oversampling factors O₁ and O₂,respectively.

FIG. 15 illustrates example orthogonal bases 1500 according toembodiments of the present disclosure. An embodiment of the orthogonalbases 1500 shown in FIG. 15 is for illustration only. One or more of thecomponents illustrated in FIG. 15 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, a UE is configured with multiple beam spacingparameters via RRC signaling, and the UE reports a preferred beamspacing parameter pair in the UE's explicit CSI report.

In some embodiments, a UE is configured to report explicit or implicitCSI feedback or eMIMO-Types depending on the rank. For instance, forrank >r, the UE reports implicit CSI and for rank ≤r, the UE reportsexplicit CSI. An example value of r is 2.

FIG. 16 illustrates an example implicit or explicit CSI based on a rank1600 according to embodiments of the present disclosure. An embodimentof the implicit or explicit CSI based on a rank 1600 shown in FIG. 16 isfor illustration only. One or more of the components illustrated in FIG.16 can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

An illustration of CSI reporting type based on rank is shown in FIG. 16. If rank ≤r, the UE derives and reports explicit CSI using the proposedexplicit CSI feedback scheme. Otherwise, the UE derives and reportsimplicit CSI using the legacy (up to Rel. 13) or future (Rel. 14 andbeyond) implicit CSI reporting schemes or eMIMO-Types.

In some embodiments, a UE is configured with a ‘Class B-E’ or ‘ClassB-Explicit’ eMIMO-Type associated with BF CSI-RS with K≥1 resources andL BF ports which are beam-formed using L basis vectors {b_(l)}. The UEderives and reports LC coefficients {c_(l)} using the coefficientcodebook (W₂) of ‘Class A-E’ or ‘Class A-Explicit’ eMIMO-Type codebook.This configuration is via RRC signaling.

If the UE is configured with K>1 BF CSI-RS resource and L ports, thenthe UE reports a CRI and corresponding LC coefficients. In suchembodiments, the eNB can determine L basis vectors {b_(l)} using UL SRSmeasurement if UL-DL duplex distance is small for FDD systems.Alternatively, eNB determines L basis vectors {b_(l)} using a DL channelprofile estimation based on CSI reports received in earlier CSIreporting instances.

FIG. 17 illustrates an example partial port explicit feedback 1700according to embodiments of the present disclosure. An embodiment of thepartial port explicit feedback 1700 shown in FIG. 17 is for illustrationonly. One or more of the components illustrated in FIG. 17 can beimplemented in specialized circuitry configured to perform the notedfunctions or one or more of the components can be implemented by one ormore processors executing instructions to perform the noted functions.Other embodiments are used without departing from the scope of thepresent disclosure.

In some embodiments, the UE is configured with a ‘Class A-E’ or ‘ClassA-Explicit’ or ‘Class B-E’ or ‘Class B-Explicit’ eMIMO-Type for partialport explicit feedback (e.g. via RRC signaling) based on the subarray orpartial port based partition of the entire 1D or 2D antenna ports, anillustration of which is shown in FIG. 17 . As shown the antenna portsare partition into 4 subarrays or partial ports. The construction ofwhich is according to the following: the number of ports in the 1stdimension of each subarray or group is M₁, where M₁ divides N₁; thenumber of ports in the 2nd dimension of each subarray or group is M₂,where M₂ divides N₂; and a subarray is 1D for 1D antenna port layoutsand is 1D or 2D for 2D antenna port layouts.

In some embodiments, the configured eMIMO-Type is associated with asingle CSI process with K=Q resources, each for M (per polarizationcase) or 2M (both polarization case) resources. In another method, theconfigured eMIMO-Type is associated with Q CSI processes with K=1resource for M (per polarization case) or 2M (both polarization case)resources.

The number of subarrays or partial ports in the dimension d=1, 2 is

$Q_{d} = {\frac{N_{d}}{M_{d}}.}$

The total number of subarrays or partial ports is Q=Q₁Q₂ and the totalnumber of antenna ports in each subarray or partial port is M=M₁M₂. LetH_(q,k) ^((I)) be the DL channel associated with the subarray or partialport index q=(q₁, q₂) where q_(d)∈{0, 1, . . . , Q_(d)−1} for d=1, 2,and q∈{0, 1, . . . , Q−1}, (I) belongs to {(f, r, p), (f, r), (f, p),(f)}, and k is a subcarrier in SB f. The UE derives and reports at leastQ explicit CSI for Q subarrays or partial ports either independently ordependently. The eNB aggregates them to reconstruct the full explicitCSI. The details of partial port explicit CSI reporting andreconstruction for Alt 0-Alt 4 are provided below.

In some embodiments of Alt 0, channel for each of Q subarrays or partialports {(q₁, q₂)_(q)}_(q=0) ^(Q-1) is reported using the same masterbasis set (W₁) and LC coefficient codebook (W₂) for all Q subarrays orpartial ports. In one example of Alt 0-0: H_(q,k) ^((I))≈Σ_(l=0)^(L-1)c_(l)b_(l), where the dimension of b_(l) is the same as H_(q,k)^((I)) depending on I. In another example of Alt 0-1: H_(q,k)^((I))≈Σ_(l=0) ^(L-1)c_(l)b_(T,l)b_(R,l) ^(H), where b_(T,l) is a columnvector of length M or 2M depending on I and b_(R,l) is a column vectorof length N_(r). The l-th basis vector is decomposed into the Tx and Rxbasis vector pair (b_(T,l), b_(R,l)).

To reconstruct the full channel, eNB first reconstructs channels for Qsubarrays or partial ports and then stacks them together according totheir indices {(q₁, q₂)_(q)}_(q=0) ^(Q-1). For example, for (Q₁, Q₂)=(2,2), the reconstructed channel is given by:

$H^{(I)} = {\begin{bmatrix}H_{({0,0})}^{(I)} & H_{({0,1})}^{(I)} \\H_{({1,0})}^{(I)} & H_{({1,1})}^{(I)}\end{bmatrix}.}$

In some embodiments of Alt 1, left (Tx) covariance matrix for each of Qsubarrays or partial ports {(q₁, q₂)_(q)}_(q=0) ^(Q-1) (total Qcovariance matrices) and left (Tx) cross-covariance matrices acrossdifferent partial ports (total

$\frac{Q\left( {Q - 1} \right)}{2}$

cross-covariance matrices) are reported using the same master basis set(W₁) and LC coefficient codebook (W₂). In such embodiments, Covariancematrix is given b:

${E_{T,q,q} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{q,k}^{(I)} \right)\left( H_{q,k}^{(I)} \right)^{H}} \right)}} \approx {\sum_{l = 0}^{L_{T} - 1}{c_{T,l}b_{T,l}b_{T,l}^{H}}}}},$

where b_(T,l) is defined in Alt 0-1, c_(T,l) is the l-th Tx coefficient,and L_(T) is the number of Tx basis vectors. In such embodiments,Cross-covariance matrix is given by

$E_{T,q,q^{\prime}} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{q,k}^{(I)} \right)\left( H_{q^{\prime},k}^{(I)} \right)^{H}} \right)}} \approx {\sum_{l = 0}^{L_{T} - 1}{c_{T,l}b_{T,l}b_{T,l}^{H}}}}$

for q>q′. In such embodiments, note that cross-covariance matrices forq<q′ are not reported because covariance matrices are symmetric, hencecross-covariance matrices are the same for the symmetric pairs (q, q′)and (q′, q). Note also that cross-covariance reporting is an example ofdependent CSI reporting across two partial ports.

To reconstruct the full covariance matrix, eNB first reconstructscovariance and cross-covariance matrices and then stacks them togetheraccording to their indices {(q₁, q₂)_(q)}_(q=0) ^(Q-1) utilizing thesymmetric property of covariance matrices. For example, for (Q₁, Q₂)=(2,1), the reconstructed covariance matric is

$E_{T} = {\begin{bmatrix}E_{T,0,0} & E_{T,1,0} \\E_{T,1,0}^{H} & E_{T,1,1}\end{bmatrix}.}$

In some embodiments of Alt 2, left and right (Tx and Rx) covariancematrices of H^((I)) is determined as where (I) belongs to {(f, p), (f)}:E_(T) same as in Alt 1; and

${E_{R} = {{\frac{1}{❘f❘}{\sum_{k \in f}\left( {\left( H_{k}^{(I)} \right)^{H}\left( H_{k}^{(I)} \right)} \right)}} \approx {\sum_{l = 0}^{L_{R} - 1}{c_{R,l}b_{R,l}b_{R,l}^{H}}}}},$

where b_(R,l) is defined in Alt 0-1, c_(R,l) is the l-th Rx coefficient,and L_(R) is the number of Rx basis vectors.

In some embodiments of Alt 3, left (Tx) dominant eigenvector of eithereach partial port channel H_(q) ^((I)) or full channel H^((I)) (obtainedafter stacking partial port channels) is reported. In case of theformer, the eNB may or may not reconstruct the eigenvector of fullchannel using that of the partial port channels. Here, e_(T,q,1) ore_(T,1)≈Σ_(l=0) ^(L) ^(T) ⁻¹c_(T,l)b_(T,l).

In some embodiments of Alt 4, left and right (Tx and Rx) dominanteigenvectors of either each partial port channel H_(q) ^((I)) or fullchannel H^((I)) (obtained after stacking partial port channels) isreported. In case of the former, the eNB may or may not reconstruct theTx eigenvector of full channel using that of the partial port channels.In one example of Alt 4-0: separate, e_(T,q,1) or e_(T,1) same as in Alt3 and e_(R,1)≈Σ_(l=0) ^(L) ^(R) ⁻¹c_(R,l)b_(R,l). In another example ofAlt 4-1: join, e_(T,q,1)e_(R,1) ^(H) or e_(T,1)e_(R,1) ^(H)≈Σ_(l=0)^(L-1)c_(l)b_(T,l)b_(R,l) ^(H).

In some embodiments, a UE is configured with one CSI process with twotypes of NZP CSI-RS resources or two CSI processes with two types of NZPCSI-RS resources wherein, 1st CSI-RS resource is either NP CSI-RS or BFCSI-RS with K₁>1 resource and 2nd CSI-RS resource is either BF CSI-RSwith K₂=1 resource or BF CSI-RS with K₂>1 resources.

The two NZP CSI-RS resources are associated with two eMIMO-Typesaccording to the configuration where supported eMIMO-Type combinationsare according to Table 9 depending on whether the two NZP CSI-RSresources correspond to implicit or explicit CSI types. For eacheMIMO-Type configuration, the exact CSI contents reported in the two CSIreports can also be configured. A few examples of CSI contents in thetwo CSI reports are shown in Table 10.

TABLE 9 Supported eMIMO-Type combinations for hybrid CSI reporting CSItype for first CSI-RS resource CSI type for second CSI-RS resource CSICSI Config. Type eMIMO-Type Type eMIMO-Type 0 Implicit Class A, Class BK₁ ≥ 1 Implicit Class A, Class B K₂ ≥ 1 1 Implicit Class A, Class B K₁ ≥1 Explicit Class A-E, Class B-E K₂ ≥ 1 2 Explicit Class A-E, Class B-EK₁ ≥ 1 Implicit Class A, Class B K₂ ≥ 1 3 Explicit Class A-E, Class B-EK₁ ≥ 1 Explicit Class A-E, Class B-E K₂ ≥ 1

TABLE 10 Example CSI reporting contents for hybrid CSI reporting CSIderived with the first CSI derived with the second CSI-RS resource (BF)CSI-RS resource CSI eMIMO- CSI CSI eMIMO- CSI Configuration Type Typecontent Type Type content Optional 0-0 Implicit Class A W₁, RI ImplicitClass B Class B 0-1 Class A W₁ (RI = 1 is K₂ = 1 W₂, assumed) RI, CQI0-2 Class B W₁ K₁ = 1 0-3 Class B CRI, W₁ K₁ > 1 0-4 Class B K₁ K₁ > 1independent W₁ reports 1-0 Implicit Class A W₁, RI Explicit Class B-EClass B-E RI, CQI 1-1 Class A W₁ (RI = 1 is K₂ = 1 W₂ assumed) 1-2 ClassB W₁ K₁ = 1 1-3 Class B CRI, W₁ K₁ > 1 1-4 Class B K₁ K₁ > 1 independentW₁ reports 2-0 - 2-4 Explicit 0-0 to 0-4 with Class A Implicit 2nd CSIreport of 0-0 to 0-4 and Class replaced with Class A-E and Class B- E,respectively 3-0 - 3-4 Explicit 1st CSI report of 2-0 to Explicit 2ndCSI report of 1-0 to 1-4 2-4

In some embodiments, a UE is configured with either explicit CSIfeedback representing a form of DL channel or implicit CSI feedbackcomprising of RI, PMI, and CQI via RRC signaling (1-bit RRC parameter).In one example, the explicit CSI feedback is configured using an RRCparameter ExplicitfeedbackEnabled When this parameter is ON, theproposed LC based explicit feedback is enabled regardless whethereMIMO-Type is ‘Class A’/‘nonPrecoded’ or ‘Class B’/‘beamformed.’ Inanother example, when the UE is configured with eMIMO-Type ‘ClassA’/‘nonPrecoded’, then the UE uses the Class A explicit feedbackproposed in the present disclosure. In yet another example, when the UEis configured with eMIMO-Type ‘Class B’/‘beamformed’, then the UE usesthe Class B explicit feedback proposed in the present disclosure. In yetanother example, when this parameter is OFF, then the UE uses Rel. 13 orRel. 14 Class A or Class B codebooks depending on the configuredeMIMO-Type.

In some embodiments, the Class A explicit feedback is configured usingan RRC parameter ClassAExplicitfeedbackEnabled. When this parameter isON and the UE is configured with eMIMO-Type ‘Class A’/‘nonPrecoded’,then the UE uses the Class A explicit feedback proposed in the presentdisclosure. When this parameter is OFF and the UE is configured witheMIMO-Type ‘Class A’/‘nonPrecoded’, then the UE uses the Rel. 13 or Rel.14 Class A codebook for CSI calculation.

In some embodiments, the Class B LC explicit feedback is configuredusing an RRC parameter ClassBExplicitfeedbackEnabled. When thisparameter is ON and the UE is configured with eMIMO-Type ‘ClassB’/‘beamformed’, then the UE uses the Class B explicit feedback proposedin the present disclosure. When this parameter is OFF and the UE isconfigured with eMIMO-Type ‘Class B’/‘beamformed’, then the UE uses theRel. 13 or Rel. 14 Class B codebook for CSI calculation.

An example of LC based explicit feedback configuration for hybrid CSI-RSand CSI reporting is shown in Table 11. In this hybrid scheme, there aretwo CSI-RS associated with two eMIMO-Types in one CSI process. Forinstance, the 1st CSI-RS is NP and is associated with Class A eMIMO-Typeand the 2nd CSI-RS is BF and is associated with Class B, K=1 eMIMO-Type.Depending on the RRC parameter value, the Class A and Class B explicitfeedback can be enabled/disabled as shown in Table 11.

The LC based explicit feedback for other hybrid CSI schemes such as 1steMIMO-Type Class B, K≥1 and 2nd eMIMO-Type Class B, K=1 can beconfigured similarly.

TABLE 11 LC based explicit feedback configuration for hybrid CSI-RSHybrid CSI Combination 1st eMIMO-Type 2nd eMIMO-Type associated with 1stassociated with 2nd (BF) RRC parameter Value (NP) CSI-RS: Class ACSI-RS: Class B,K = 1 CombinationCBEnabled ON Class A Explicit Class BLC Explicit OFF Rel. 13 or Rel. 14 Class Rel. 13 or Rel. 14 Class B AImplicit Implicit ClassACombinationCBEnabled ON Class A LC Explicit Rel.13 or Rel. 14 Class B OFF Rel. 13 or Rel. 14 Class Implicit A ImplicitClassBCombinationCBEnabled ON Rel. 13 or Rel. 14 Class Class B LCExplicit OFF A Implicit Rel. 13 or Rel. 14 Class B Implicit

FIG. 18 illustrates example W₁ codebook alternatives 1800 according toembodiments of the present disclosure. An embodiment of the W₁ codebookalternatives 1800 shown in FIG. 18 is for illustration only. One or moreof the components illustrated in FIG. 18 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

In some embodiments, a UE is configured with either implicit CSIfeedback (for low spatial resolution feedback) or explicit CSI feedback(for high spatial resolution feedback) (via RRC signaling) based on adual-stage codebook structure W=W₁W₂, where W₁ codebook for the twotypes of CSI feedback is according to one of the following alternatives:common W₁: the W₁ codebook is common between implicit and explicit CSIfeedback; different W₁: the W₁ codebook for implicit CSI feedback isdifferent from that for explicit CSI feedback; or subset W₁: the W₁codebook for implicit CSI is a subset of that for explicit CSI feedback.An illustration of the three W₁ codebook alternatives is shown in FIG.18 , where the W₁ codebook is according to some embodiments of thispresent disclosure, for example, Rel. 13 Class A W₁ codebook (e.g.,Table 7 or a new W₁ codebook proposed in the present disclosure.

The W₂ codebook for implicit CSI feedback is according to legacy (up toRel. 13 or Rel. 14) codebooks. For example, the W₂ codebook in Rel. 13is a Class A codebook. Alternatively, the W₂ codebook is a new W₂codebook.

The W₂ codebook for explicit CSI feedback is according to someembodiments of the present disclosure. In addition, it may or may notinclude the W₂ codebook for implicit CSI feedback. For example, the W₂codebook for explicit CSI feedback comprises of the W₂ codebook forimplicit CSI feedback and a new W₂ codebook for explicit CSI feedbackproposed in the present disclosure.

In one embodiment, the Rel. 13 Class A codebook parameterCodebook-Config is used to configure implicit or explicit CSI feedback.For example, when Codebook-Config=1, then the UE is configured withimplicit feedback, and Codebook-Config=2, 3, 4, then the UE isconfigured with explicit feedback. This is an example of different W₁codebook for types of CSI feedback.

In another embodiment, a new RRC parameter such ExplicitfeedbackEnabled(or other parameters mentioned above) is used to configure implicit orexplicit CSI feedback according to the previous embodiment. In suchembodiment, all three alternatives of W₁ codebook are possible. In oneexample of common W₁, Rel. 13 Class A W₁ codebook for Codebook-Config=2,3, or 4 is used regardless of the configured CSI type (e.g.,ExplicitfeedbackEnabled is turned ON or OFF). In another example ofdifferent W₁, Rel. 13 Class A W₁ codebook for Codebook-Config=2, 3, or 4is used if implicit CSI feedback is configured (e.g.,ExplicitfeedbackEnabled is turned OFF), and a new W₁ codebook is used ifexplicit CSI feedback is configured (e.g., ExplicitfeedbackEnabled isturned ON). In yet another example of subset W₁, Rel. 13 Class A W₁codebook for Codebook-Config=2, 3, or 4 is used if implicit CSI feedbackis configured (e.g., ExplicitfeedbackEnabled is turned OFF), and a newW₁ codebook which includes Rel. 13 Class A W₁ codebook is used ifexplicit CSI feedback is configured (e.g., ExplicitfeedbackEnabled isturned ON).

If I={(f) (f r)}, the W₂ codebook has two components. In one example,Co-phase {φ_(l)}_(l=0) ^(L-1): it is reported In this case, LC beamswith co-phase are given by

$\left\{ {{{\begin{bmatrix}b_{l} \\{\varphi_{l}b_{l}}\end{bmatrix}:l} = 0},1,\ldots,{L - 1}} \right\},$

where the co-phase φ_(l) belongs to {1,j,−1,−j}, for example. In suchexample, there are two alternatives for the co-phase: common: sameco-phase for L beams; and Different: different co-phase for L beams. Inanother example, Coefficients {c_(l)}_(l=0) ^(L-1), the un-quantized LCcoefficients can be obtained as the least-square solution to minimizethe squared error. For example, for eigenvector feedback, theun-quantized coefficients are

$\left\{ c_{l} \right\}_{l = 0}^{L - 1} = {\arg\min\limits_{{\{ c_{l}\}}_{l = 0}^{L - 1}}{{{e - {\sum_{l = 0}^{L - 1}{c_{l}\begin{bmatrix}b_{l} \\{\varphi_{l}b_{l}}\end{bmatrix}}}}}^{2}.}}$

The resultant solution is obtained by pre-multiplying the dominanteigenvector e with the pseudo-inverse of the basis vector set, i.e.,{c_(l)}_(l=0) ^(L-1)=(B*B)⁻¹B*e, where

$B - \left\lbrack {\begin{matrix}b_{0} \\{\varphi_{0}b_{0}}\end{matrix},\begin{matrix}b_{1} \\{\varphi_{1}b_{1}}\end{matrix},\ldots,\begin{matrix}b_{L - 1} \\{\varphi_{L - 1}b_{L - 1}}\end{matrix}} \right\rbrack$

is basis matrix in which columns are basis vectors.

In some embodiments, the W₂ codebook has one component for thecoefficient. The un-quantized coefficient in this method can be obtainedas {c_(l)}_(l=0) ^(L-1)=(B*B)⁻¹B*e, where

$B = {\begin{bmatrix}\begin{matrix}b_{0} & b_{1} & \ldots & b_{L - 1}\end{matrix} & 0 \\0 & \begin{matrix}b_{0} & b_{1} & \ldots & b_{L - 1}\end{matrix}\end{bmatrix}.}$

If I={(f, p), (f, r, p)}, then the W₂ codebook is for the coefficient.The un-quantized coefficient is obtained as {c_(l)}_(l=0)^(L-1)=(B*B)⁻¹B*e, where B=[b₀ b₁ . . . b_(L-1)].

In some embodiments, a UE is configured with a single (complex)coefficient codebook W₂ which quantizes the complex coefficients {c_(l):l=0, 1, . . . , L−1} and reports the quantized coefficients per SB.

In some embodiments, a UE is configured with a coefficient codebook W₂which can be decomposed into a double codebook: magnitude W_(2,mag) isfor the magnitude of coefficients, i.e., {|c_(l): l=0, 1, . . . , L−1};and phase W_(2, ph) is for the phase of coefficients, i.e., {α_(l): l=0,1, . . . , L−1} where c_(l)=|c_(l)|e^(iα) ^(l) is the magnitude andphase representation of l-th coefficient. The UE is further configuredto report the magnitudes and phases of the coefficients according to oneof the following sub-embodiments.

In some embodiment, the UE is configured to report magnitudes and phasesof coefficients separately where the magnitude reporting is WB, i.e.,the UE reports only one magnitude vector for all SBs comprising the WBand the phase reporting is per SB, i.e., the UE reports a phase vectorfor each SB.

In one example, magnitude codebook is Constant modulus, for example

${❘c_{l}❘} = \frac{1}{\sqrt{L}}$

wherein no WB indication is needed in this case. In another example,magnitude codebook is B-bit uniform codebook over [0, U], where U is afinite positive number. In one example value of B is 4.

An example of phase codebook is C-PSK codebook. One example value of Cis 4 (QPSK codebook) which corresponds to 2-bit quantization. Anotherexample value of C is 8 (8-PSK codebook) which corresponds to 3-bitquantization. Another example of phase codebook is an oversampled DFTcodebook of length L and appropriate oversampling factor O (e.g. 8, 16).

In some embodiments, the UE is configured to report magnitudes andphases of coefficients separately where the magnitude reporting isdifferential in two stages. In one example, stage 0: WB magnitude isreported, i.e., |c_(l)| is quantized as d_(l,WB) using a 4-bit uniformcodebook, for example; and (2) stage 1: Per SB magnitude is reported,i.e., |c_(l)|−d_(l,WB) is quantized using a 2-bit uniform codebook, forexample. In another example, the phase reporting is per SB as inSub-embodiment 1.

In some embodiments, the Stage 0 for magnitude reporting corresponds toone WB magnitude for all L coefficients, i.e., one d_(l,WB) is reportedfor all l=0, 1, . . . , L−1. In one embodiment, the Stage 0 correspondsto separate WB magnitude for each of L coefficients.

In some embodiments, the UE is configured to report a WB norm value,denoted as K, for the coefficients, an example of which is the Euclideannorm K=√{square root over (∥Σ_(l=0) ^(L-1)|c_(l)|²∥)}. In one example,the norm is quantized using a N_(K)-bit uniform codebook over [0,U],where U is a finite positive number. An example value for N_(K) is 16.

The UE is also configured to report the normalized coefficients

$\left\{ {{{\frac{c_{l}}{K}:l} = 0},1,\ldots,{L - 1}} \right\}.$

Note that the normalized coefficient vector lies on a complexunit-sphere in an L-dimensional complex Euclidean space. The magnitudesand phases of the normalized coefficients can be reported according tothe above-mentioned embodiments or sub-embodiments. In particular, themagnitudes of normalized coefficients can be reported WB or per SB usinga B-bit uniform codebook over (0, 1), where an example value for B is 2,and the phases of normalized coefficients can be reported per SB usingeither QPSK or 8-PSK codebooks.

In some embodiments, the UE is configured to report: magnitudes of thecoefficients according to some embodiments or sub-embodiments of thispresent disclosure, and phases of the coefficients using a two stagephase codebook C_(co-ph)=C_(co-ph,1)C_(co-ph,2), where C_(co_ph,1) isfor WB phase reporting and C_(co-ph,2) is for SB phase reporting. Anexample of such as codebook is

$C_{{{co} - ph},1} = {{\begin{Bmatrix}e^{\frac{j\pi}{4}} & e^{\frac{j3\pi}{4}} & e^{\frac{j5\pi}{4}} & e^{\frac{j7\pi}{4}}\end{Bmatrix}{and}C_{{{co} - ph},2}} = {\begin{Bmatrix}e^{\frac{j\pi}{4}} & e^{- \frac{j\pi}{4}}\end{Bmatrix}.}}$

In some embodiments, a UE first performs a dimension reduction of LCcoefficients across SBs and across different coefficients, and thenquantizes the reduced dimensional coefficients using the W₂ codebookaccording to some embodiments of the present disclosure.

In one example of dimension reduction, the coefficient matrix for S SBsand L coefficients is expressed as:

$C = \begin{bmatrix}c_{0,0} & c_{0,1} & \ldots & c_{0,{L - 1}} \\c_{1,0} & c_{1,1} & \ldots & c_{1,{L - 1}} \\ \vdots & \vdots & \ddots & \vdots \\c_{{S - 1},0} & c_{{S - 1},1} & \ldots & c_{{S - 1},{L - 1}}\end{bmatrix}$

where row s corresponds L coefficients for SB s and column l correspondsto S SBs for coefficient l. The singular value decomposition of C isperformed C=UΣV^(H)=Σ_(i=0) ^(D-1)σ_(i)u_(i)v_(i) ^(H), where U=[u₀ u₁ .. . u_(S-1)] is the left eigenvector matrix (columns are length-Seigenvectors); V=[v₀ v₁ . . . v_(L-1)] is the right eigenvector matrix(columns are length-L eigenvectors); Σ=diag([σ₀ σ₁ . . . σ_(D-1)]) is adiagonal matrix of singular values sorted as σ₀≥σ₁≥ . . . ≥σ_(D-1), andD=min(S, L).

Then, d where 1≤d<D ‘dominant’ singular values σ₀, . . . σ_(d) areselected and corresponding left and right eigenvector matrices can beconstructed as: U_(d)=[u₀ u₁ . . . u_(d)]; V_(d)=[v₀ v₁ . . . v_(d)];and Σ_(d)=diag([σ₀ σ₁ . . . σ_(d)].

The reduced dimensional coefficient matrix is then given byC≅C_(d)=U_(d)Σ_(d)V_(d) ^(H)=Σ_(i=0) ^(d)σ_(i)u_(i)v_(i) ^(H).

To obtain reduced dimensional coefficients, the UE transforms thecoefficient matrix C as R_(d)=CV_(d). The UE then quantizes R_(d) andV_(d) using the W₂ codebook and sends the quantized matrices to the eNB,which reconstructs the coefficient matrix as C=R_(d)V_(d) ^(H).

In some embodiments, the d value is configured to the UE. In someembodiments, the UE reports a value. In some embodiments, the d value isfixed, for example to 1.

In some embodiments, a UE performs other forms of dimension reductiontransformations on coefficient matrix C and reports the transformedcoefficients using the W₂ codebook according to some embodiments of thispresent disclosure. A few examples of other transformation include 1D or2D Discrete Cosine Transform (DCT), 1D or 2D discrete Fourier transform(DFT), and Karhunen-Loève Transform (KLT).

In some embodiments, the dimension reduction is applied by constructinghigher dimensional coefficient matrix C by including more dimensionssuch as (e.g., SB, coefficient, time). In some embodiments, thedimension reduction is applied only across SBs or only acrosscoefficients.

In some embodiments, a UE is configured with at least one L value forClass A-E or B-E explicit codebook, and one (L₁, L₂) pair for hybridexplicit codebook via higher-layer RRC signaling, where the set ofconfigurable L or (L₁ or/and L₂) values includes 2, 4, and 8.

In some embodiments, the L or (L₁ or/and L₂) beams or basis vectorsassociated with the configured L or (L₁ or/and L₂) value arepre-determined and fixed.

In some embodiments, the UE is configured with Codebook-Config (similarto Rel. 13 Class A codebook parameter), where the set of configurableCodebook-Config values include 1, 2, 3, and 4. For example, anillustration of mapping Codebook-Config to L or (L₁ or/and L₂) beams orbasis vectors is shown in FIGS. 29 and 30 .

In some embodiments, a UE is configured with multiple L values via RRCsignaling which may be a subset of {2, 4, 8}. The UE reports a preferredL value from the configured set, where this report may either be: WB inwhich the number of beams or basis vectors remains the same in all SBsor SB in which the number of beams or basis vectors may change indifferent SBs.

In some embodiments, a UE is configured with either: implicit CSIcodebook: such as up to Rel. 13 codebooks, and Rel. 14 codebooks or theproposed explicit CSI codebook using a 1-bit RRC signaling.

FIG. 19 illustrates example master beam groups 1900 according toembodiments of the present disclosure. An embodiment of the master beamgroups 1900 shown in FIG. 19 is for illustration only. One or more ofthe components illustrated in FIG. 19 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, a UE is configured with an oversampled DFT codebookas the master basis set comprising of O₁N₁×O₂N₂ DFT beams and (L₁, L₂)parameters representing the number of beams in the two dimensions of themaster beam group.

The UE is further configured with multiple types of master beam groupsbased on the spacing (p₁, p₂) between two adjacent beams in twodimensions of the master beam group. The UE reports one of multipletypes of master beam groups in the UE's CSI report where this reportingcan be explicit as a new WB CSI feedback component or it is implicitwith either i₁ or (i_(1,1), i_(1,2)). An illustration of two types ofmaster beam groups is shown in FIG. 18 , where each small squarerepresents a 2D DFT beam. When (p₁, p₂)=(1, 1), the master beam groupcorresponds to L₁L₂ closely spaced beams, and when (p₁, p₂)=(O₁, O₂),the master beam group corresponds to L₁L₂ orthogonal beams. Threeexamples of master beam groups for each type are also shown as BG0, BG1,and BG2.

Alternatively, eNB configures one of multiple types of master beamgroups via RRC signaling. For example, eNB configures one of the twomaster beam groups shown in FIG. 18 via 1-bit RRC parameterMasteBeamGroupType.

In some embodiments, the explicit CSI report comprises a master beamgroup of configured or reported type is reported as the 1st PMI i₁ or(i_(1,1), i_(1,2)). This reporting is WB. The range of values of i_(1,1)and i_(1,2) is given by i_(1,1)=0, 1, 2, . . . O₁N₁/s₁ and i_(1,2)=0, 1,2, . . . O₂N₂/s₂, where (s₁,s₂) are spacing between two adjacent masterbeam groups in two dimensions. The example values of s₁ (or s₂) are 1,2, O₁/4 (or O₂/4), O₁/2 (or O₂/2), and O₁ (or O₂). So, the number ofbits to report is log₂

$\left\lceil \frac{O_{1}N_{1}}{s_{1}} \right\rceil{and}\log_{2}{\left\lceil \frac{O_{2}N_{2}}{s_{2}} \right\rceil.}$

In some embodiments, the explicit CSI report, for each SB in which theUE is configured to report explicit CSI, comprises a beam selection: Lout L₁L₂ beams are selected from the reported master beam group.Examples of L values are 2, 4, and 8. The L value can be reported in theCSI report or it is configured via higher layer RRC signaling. In thecase of the former, the reported L value is either WB or SB. In oneexample, the selection is parameterized: the selection of L beams isbased on Config parameter. Examples of a few beam selections are shownin FIG. 20 . In such example, the UE reports a preferred Config value inper SB CSI report where the set of possible Config values is fixed, forexample Config 0-16 in FIG. 20 . In such example, the UE reports a WB Lvalue and a Config value per SB corresponding to the reported L. Forexample, the UE reports L=2 in the WB CSI report (2-bit WB reporting ofan L value) and reports one of Config 0-Config 3 in per SB CSI report(2-bit SB reporting on Config). Alternatively, an L value is configuredvia RRC signaling and the UE reports a Config value corresponding to thereported L. In such example, the set of Config values for per SB beamselection is configured via RRC signaling. For example, a length 17bitmap is used to configure the set of Config values (e.g., FIG. 20 ).

In another example, the selection is unconstrained: The selected L beamsis unconstrained and any L out of L₁L₂ beams can be reported. In thiscase, the reporting can be based on a bitmap of length L₁L₂.

In some embodiments, the explicit CSI report, for each SB in which theUE is configured to report explicit CSI, comprises Co-phase: K-PSK (e.g.QPSK) co-phase for two polarizations can also be reported.

In some embodiments, the explicit CSI report, for each SB in which theUE is configured to report explicit CSI, comprises coefficients:Coefficients to linearly combine L selected beams are reported.

FIG. 20 illustrates an example beam selection 2000 according toembodiments of the present disclosure. An embodiment of the beamselection 2000 shown in FIG. 20 is for illustration only. One or more ofthe components illustrated in FIG. 20 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, the UE is configured with a DFT codebook withoutoversampling (e.g. oversampling factor=1). As in the previousembodiment, the UE reports a master beam group comprises of L₁L₂ beams(WB) and for each SB, reports L out of L₁L₂ reported beams. In addition,the UE also reports the rotation matrix (M) for either each of L beams(L rotation matrices) or the whole beam group (one rotation matrix),where the rotation can be WB or SB, and it can be only in one dimensionor in both dimensions. An example of rotation matrix is a diagonalmatrix whose diagonal entries form a DFT vector.

In some embodiments, a UE is configured with an explicit CSI reportingin which the proposed LC framework for explicit CSI reporting isextended to include frequency dimension in addition to the 1st and 2ndport dimensions. An illustration of the master grid of beams in 3D (1stport dim., 2nd port dim., freq. dim.) is shown in FIG. 20 in which: 1stdimension is associated with the 1st port dimension; 2nd dimension isassociated with the 2nd port dimension; and 3rd dimension is associatedwith the frequency dimension.

The master basis set for spatial (port) domain representation, (i.e.,1st and 2nd dimensions) is according to some embodiments of this presentdisclosure. In particular, it is according to the aforementionedembodiments of Alt 0-Alt 4 for DL channel or derivatives explainedearlier in the present disclosure. The master basis set for frequencydomain representation (i.e., 3rd dimension) is an oversampled DFTcodebook of length-N₃ and with oversampling factor O₃. Some examplevalues for the oversampling factors O₃ include {2, 4, 8}. The length N₃depends on the type of frequency domain representation. Some examples ofwhich are shown FIG. 20 .

FIG. 21 illustrates example frequency domain representation alternatives2100 according to embodiments of the present disclosure. An embodimentof the frequency domain representation alternatives 2100 shown in FIG.21 is for illustration only. One or more of the components illustratedin FIG. 21 can be implemented in specialized circuitry configured toperform the noted functions or one or more of the components can beimplemented by one or more processors executing instructions to performthe noted functions. Other embodiments are used without departing fromthe scope of the present disclosure.

TABLE 12 Frequency domain representation alternatives Frequency domainN₃ representation Eigenvector or covariance type Channel matrix PRB 1 1number of subcarriers in each 1 PRB SB number of PRBs in each SB 1number of subcarriers in each number of PRBs in each SB PRB × number ofPRBs in each SB WB number of PRBs in each SB x number of SBs in whole BWnumber of SBs in whole BW number of subcarriers in each number of PRBsin each SB × PRB × number of PRBs in number of SBs in whole BW each SB ×number of SBs in whole BW Best P PRBs P P number of subcarriers in eachP PRB × P

In some embodiments, a UE is configured with a ‘Class E’ or ‘ClassExplicit’ eMIMO-Type in which DL channel or one of derivatives isreported based on the extended LC framework as Σ_(m=0) ^(M-1)Σ_(l=0)^(L-1)c_(m,l)(a_(m)b_(l) ^(H)) or Σ_(m=0) ^(M-1)Σ_(l=0)^(L-1)c_(m,l)(a_(m)⊗b_(l)) using a double codebook for explicitfeedback: W=W₁W₂, where W₁ is for WB and long-term feedback of two basisvector sets: {a_(m): m=0, 1, . . . , M−1} for frequency domain (acrossSBs) representation; and {b_(l): l=0, 1, . . . , L−1} for spatial domain(across number of Tx (and Rx antennas)) representation, W₂ is for SB andshort-term LC coefficients {c_(m,l): m=0, 1, . . . , M−1 and l=0, 1, . .. , L−1} feedback, and M and L, respectively are the size of the twobasis vector sets in frequency and spatial domains. An illustration of afew example W₁ bases according to this embodiment is shown in FIG. 21 .

FIG. 22 illustrates an example W₁ beams or basis 2200 according toembodiments of the present disclosure. An embodiment of the W₁ beams orbasis 2200 shown in FIG. 22 is for illustration only. One or more of thecomponents illustrated in FIG. 22 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, {a_(m): m=0, 1, . . . , M−1} is reported jointlywith {b_(l): l=0, 1, . . . , L−1} in the 1st PMI i₁ or in the firstcomponent of the 1st PMI i_(1,1), or in the second component of the 1stPMI i_(1,2).

In some embodiments, {a_(m): m=0, 1, . . . , M−1} and {b_(l): l=0, 1, .. . , L−1} are reported separately. In particular, {b_(l): l=0, 1, . . ., L−1} is reported as the 1st PMI i₁ or (i_(1,1), i_(1,2)), and {a_(m):m=0, 1, . . . , M−1} is reported as another 1st PMI i₁ ⁽⁰⁾. In thismethod, the W₁ codebook can be represented as W₁=W₁ ⁽⁰⁾W₁ ⁽¹⁾ where W₁⁽⁰⁾ is used for i₁ ⁽⁰⁾ reporting and W₁ ⁽¹⁾ is used for i₁ or (i_(1,1),i_(1,2)) reporting.

In some embodiments, {c_(m,l): m=0, 1, . . . , M−1 and l=0, 1, . . . ,L−1} is reported jointly as the second PMI i₂ using a single codebookaccording to some embodiments of this present disclosure.

In some embodiments, {c_(m,l): m=0, 1, . . . , M−1 and l=0, 1, . . . ,L−1} can be decomposed as c_(m,l)=c_(m)×c_(l), and {c_(m): m=0, 1, . . ., M−1} and {c_(l): l=0, 1, . . . , L−1} are reported using two separatecodebooks, where the two codebooks may or may not be the same. Thereporting of two sets of coefficients can be joint as the second PMI i₂.Alternatively, the reporting of two sets of coefficients can be separateas the second PMI i₂ for {c_(l): l=0, 1, . . . , L−1} and as anothersecond PMI i₂ ⁽⁰⁾ for {c_(m): m=0, 1, . . . , M−1}. In this lateralternative, the W₂ codebook can be represented as W₂=W₂ ⁽⁰⁾W₂ ⁽¹⁾ whereW₂ ⁽⁰⁾ is used for i₂ ⁽⁰⁾ reporting and W₂ ⁽¹⁾ is used for i₂ reporting.

In some embodiments, a UE is configured with a ‘Class E’ or ‘ClassExplicit’ eMIMO-Type in which DL channel or one of derivatives isreported based on the extended LC framework as Σ_(l=0)^(L-1)c_(l)(a_(l)b_(l) ^(H)) or Σ_(l=0) ^(L-1)c_(l)(a_(l)⊗b_(l)) using adouble codebook for explicit feedback: W=W₁W₂, where W₁ is for WB andlong-term feedback of a joint basis vector set for both frequency andspatial domain representations comprising of either: basis matrices{a_(l)b_(l) ^(H): l=0, 1, . . . , L−1} or basis vectors {a_(l)⊗b_(l):l=0, 1, . . . , L−1}, where {a_(m): m=0, 1, . . . , L−1} is forfrequency domain (across SBs) representation and {b_(l): l=0, 1, . . . ,L−1} is for spatial domain (across number of Tx (and Rx antennas))representation, W₂ is for SB and short-term LC coefficients {c_(l): l=0,1, . . . , L−1} feedback, and L is the size of the basis vector set.

In some embodiments, the master basis set component for spatial domainrepresentation {b_(l): l=0, 1, . . . , L−1} is according to someembodiments of the present disclosure. In particular, it is according tothe aforementioned embodiments of Alt 0-Alt 4 for DL channel orderivatives explained earlier in the present disclosure. In someembodiments, it is different and depends on the master basis setcomponent for frequency domain representation {a_(l): l=0, 1, . . . ,L−1}. The codebook for coefficient reporting and coefficient reportingalternatives are according to some embodiments of the presentdisclosure.

In some embodiments, the UE is configured to report multiple beam groupsor basis sets (or 1st PMIs) from the W₁ codebook for explicit feedback,where multiple basis sets are reported using the same or different W₁codebook. The basis sets are according to some embodiments of thispresent disclosure. For example, the basis sets can be in two portdimensions only (1st and 2nd port dimensions) or the basis sets can bein both port and frequency dimensions. There are at least the followingthree alternatives for multiple basis set reporting.

In one example, in frequency domain, the whole system BW is partitionedinto multiple parts, where parts may or may be overlapping, and onebasis set is reported for each part. For example, a basis set isreported for each of two non-overlapping and contiguous sets of SBscovering the whole BW. In another example, in spatial domain, multiplebasis sets are reported for multiple dominant channel clusters inspatial domain. This reporting is for the whole BW (WB reporting). Forexample, two basis sets are reported for two dominant channel clusters.In yet another example, in both frequency and spatial domain, the wholesystem BW is partitioned into multiple parts, where parts may or may beoverlapping, and multiple basis sets are reported for each part. Forexample, two basis sets are reported for each of two non-overlapping andcontiguous sets of SBs covering the whole BW.

The configuration of multiple basis sets reporting is via higher-layerRRC parameter MultipleW1Enabled. If this parameter is ON, then the UEreports multiple basis sets. The number of basis sets (denoted as J) iseither fixed for example to 2 or configured from a set, an example ofwhich is {2, 3}. Similarly, the alternative for multiple basis setreporting is either fixed for example to frequency domain reporting orit is configured for example to one of frequency or spatial domainreporting.

Alternatively, the UE reports the number of basis set (J value) in theCSI report. For example, if the set of possible J values is {1, 2}, thenthe UE reports a preferred J value using 1-bit indication in CSI report.

In some embodiments, a UE is configured with one or both of the twotypes of CSI-RS resources. In one example, the “first non-zero-power(NZP) CSI-RS resource” corresponds to either: (1) full port, whereCSI-RS is transmitted from all 2N₁N₂ ports and it is non-precoded (NP)or Class A eMIMO-Type, or Partial port, where CSI-RS is transmitted froma subset of 2N₁N₂ ports, and the CSI-RS is either: NP CSI-RS or Class AeMIMO-Type or beam-formed (BF) CSI-RS or Class B eMIMO-Type with K₁≥1resources. In another example, the “second NZP CSI-RS resource”corresponds to a BF CSI-RS or Class B eMIMO-Type with either K₂=1resource or K₂>1 resources.

In some embodiments, the configured first CSI-RS has one component foreach of the two dimensions. For 1D antenna port configurations, thefirst CSI-RS has one component, and for 2D antenna port configurations,the first CSI-RS has two components: first CSI-RS 1 or first CSI-RScomponent 1; and first CSI-RS 2 or first CSI-RS component 2.

In some embodiments, the configured second CSI-RS has one component foreach of the two dimensions. For 1D antenna port configurations, thesecond CSI-RS has one component, and for 2D antenna port configurations,the second CSI-RS has two components: second CSI-RS 1 or second CSI-RScomponent 1; and second CSI-RS 2 or second CSI-RS component 2.

In some embodiments, the full-port first CSI-RS resource is alsoreferred to as Class A CSI-RS or eMIMO-Type, the partial-port firstCSI-RS resource is also referred to as Class B (K>1) CSI-RS oreMIMO-Type, and the second CSI-RS resource is also referred to as ClassB CSI-RS or eMIMO-Type.

In LTE Rel. 13, the following CSI reporting types or eMIMO-Type aresupported: ‘Class A’ eMIMO-Type in which “First CSI-RS resource” isfull-port, NP and CSI is reported using Class A codebook; and ‘Class B’eMIMO-Type in which “Second CSI-RS resource” is beamformed and CSI isreported using Class B codebook, where K=1: CQI, PMI, RI feedback andK>1: CRI, CQI, PMI, RI feedback.

In LTE Rel. 13 ‘Class A’ eMIMO-Type, a UE is configured with a CSIprocess comprising of a “first” CSI-RS resource for all 2N₁N₂ ports.Upon receiving the CSI-RS for these ports, the UE derives and feeds backthe Class A CSI feedback content comprising of the first PMI index pair,(i_(1,1), i_(1,2)), the second PMI index i₂, CQI, and RI. An exemplaryuse case of the Class A CSI feedback scheme is described in FIG. 10 .The UE derives the two PMIs using the Class A PMI codebook.

FIG. 23 illustrates an example Class A CSI feedback scheme 2300according to embodiments of the present disclosure. An embodiment of theClass A CSI feedback scheme 2300 shown in FIG. 23 is for illustrationonly. One or more of the components illustrated in FIG. 23 can beimplemented in specialized circuitry configured to perform the notedfunctions or one or more of the components can be implemented by one ormore processors executing instructions to perform the noted functions.Other embodiments are used without departing from the scope of thepresent disclosure.

In LTE Rel. 13 ‘Class B’ eMIMO-Type, a UE is configured with a CSIprocess comprising of a “second” CSI-RS resource for a subset of 2N₁N₂ports. For example, the number of configured ports is 2. Upon receivingthe CSI-RS for these ports, the UE derives and feeds back the Class BCSI feedback content comprising of a single PMI i, CQI, and RI. Anexemplary use case of the Class B CSI feedback scheme is described inFIG. 24 . The UE derives the PMI using the Class B PMI codebook.

FIG. 24 illustrates an example Class B CSI feedback scheme 2400according to embodiments of the present disclosure. An embodiment of theClass B CSI feedback scheme 2400 shown in FIG. 24 is for illustrationonly. One or more of the components illustrated in FIG. 24 can beimplemented in specialized circuitry configured to perform the notedfunctions or one or more of the components can be implemented by one ormore processors executing instructions to perform the noted functions.Other embodiments are used without departing from the scope of thepresent disclosure.

Note that the CSI-RS overhead with the Class A CSI feedback scheme islarge, which may lead to performance loss. The overhead is small forClass B CSI feedback scheme, but the overhead relies on the availabilityof beam-forming weights to beam-form Class B CSI-RS. The beam-formingweights may be obtained from UL SRS measurements assuming UL-DL duplexdistance is small. Alternatively, it may be obtained through a Class Afeedback configured with larger periodicity. The later alternative is anexample of “Hybrid” CSI feedback scheme which is the focus of thepresent disclosure.

An issue with the Class A CSI feedback scheme for the future generationof communication systems (LTE Rel. 14 and beyond, 5G), is the increasein CSI-RS overhead to support larger number of antenna ports. Inparticular, as the number of supported antenna ports increases beyond acertain number, i.e. 32, the number of supported antenna ports can't betransmitted and measured in the same subframe. Hence, CSI-RStransmission and reception will require multiple subframes, which maynot be desirable in practice.

Another issue with the Class A CSI feedback scheme is that the increasein overhead is unclear to bring justifiable performance benefits. Inother words, to achieve certain performance, it may not be necessary totransmit CSI-RS from all 2N₁N₂ ports in every CSI-RS transmissioninstance as is the case with Class A CSI feedback scheme. The sameperformance may perhaps be achieved by a so-called “hybrid CSI feedbackscheme” in which there are two types of CSI-RS resources, the firstCSI-RS resource is transmitted from all or a subset of 2N₁N₂ ports witha larger periodicity and the second CSI-RS resource is transmitted fromfewer than 2N₁N₂ ports, e.g. 2, with a smaller periodicity. The twoCSI-RS resources are associated with two CSI reporting or eMIMO-Types.

The hybrid CSI feedback scheme and hybrid eMIMO-Type alternatives areproposed. The focus of the present disclosure is the details about someof the candidate hybrid eMIMO-Type alternatives and reported CSIcontents.

In some embodiments, a UE is configured with either one CSI process withtwo NZP CSI-RS resources (each of the two associated with an eMIMO-Type)or two CSI processes each with one NZP CSI-RS resource associated withan eMIMO-Type, where 1st CSI-RS resource is associated with either ClassA eMIMO-Type or Class B eMIMO-Type with K₁≥1 resource, in terms of usecases, these two alternatives correspond to non-precoded (NP) CSI-RS andpartial-port CSI-RS, respectively, and 2nd CSI-RS resource is associatedwith Class B eMIMO-Type with K₂≥1 resources.

The two NZP CSI-RS resources are associated with two eMIMO-Typesaccording to the configuration where examples of supported eMIMO-Typecombinations are according to Table 13. The RI reported in the 1steMIMO-Type is denoted as RI⁽¹⁾ and that reported in the 2nd eMIMO-Typeis denoted as RI⁽²⁾.

Some of these configurations such as Configuration 0 have multiplealternatives such as a, b, and c depending on CSI reporting contents. Inone method, one of these alternatives is configured to the UE viahigher-layer RRC signaling. In another method, the alternative is fixed,for example, 0-a, and hence does not need to be configured.

TABLE 13 Supported eMIMO-Type combinations for hybrid CSI reporting CSIderived CSI derived with the with the first CSI-RS second (BF) CSI-RSresource resource eMIMO- eMIMO- CSI reporting Configuration Type CSIreporting content Type content 0 0-a Class A i₁ or (i_(1,1), i_(1,2)),RI⁽¹⁾ Class B CQI, PMI 0-b i₁ or (i_(1,1), i_(1,2)) K₂ = 1 RI⁽²⁾, CQI,PMI 0-c i₁ or (i_(1,1), i_(1,2)), RI⁽¹⁾ RI⁽²⁾, CQI, PMI 1 1-a Class BPMI (Alt0: Rel. 13 Class B Class B RI⁽²⁾, CQI, PMI codebook Altl: Rel.12 codebooks) 1-b K₁ = 1 CQI, RI⁽¹⁾, PMI (Alt0: Rel. K₂ = 1 RI⁽²⁾, CQI,PMI 13 Class B codebook Alt1: Rel. 12 codebooks) 2 2-a Class B CRI ClassB RI⁽²⁾, CQI, PMI 2-b K₁ > 1 PMI (Alt0: Rel. 13 Class B K₂ = 1 RI⁽²⁾,CQI, PMI codebook Altl: Rel. 12 codebooks)/RI⁽¹⁾ for each CSI-RSresource 3 3-a Class B i₁ or (i_(1,1), i_(1,2)) Class B CRI, and {RI⁽²⁾,K₁ = 1 K₂ > 1 CQI, PMI} conditioned on CRI 4 3-a Class A i₁ or (i_(1,1),i_(1,2)) Class B CRI, and {RI⁽²⁾, CQI, PMI} conditioned on CRI 3-b i₁ or(i_(1,1), i_(1,2)), RI⁽¹⁾ K₂ > 1 CRI, and {RI⁽²⁾, CQI, PMI} conditionedon CRI

In some embodiments, a UE is configured with a hybrid CSI reporting inwhich the 1st eMIMO-Type is Class A and the 2nd eMIMO-Type is Class B,K=1. The CSI reported in the Class A eMIMO-Type includes i₁ or (i_(1,1),i_(1,2)) and that reported in Class B eMIMO-Type includes CQI and PMI.Depending on whether both or at least one of RI⁽¹⁾ and RI⁽²⁾ arereported, we have the following alternatives (as shown in Table 13):0-a: Only RI⁽¹⁾ is reported; 0-b: Only RI⁽²⁾ is reported; and 0-c: BothRI⁽¹⁾ and RI⁽²⁾ are reported.

The UE is configured with the Rel. 13 Class B codebook (or extension inRel. 14) for the Class B eMIMO-Type. Alternatively, the UE is configuredwith a new codebook for the Class B eMIMO-Type.

In the following embodiments, Rel. 13 Class A and Class B codebooks areassumed for two eMIMO-Types as examples. The embodiments, however, areapplicable to other Class A and Class B codebooks such as the linearcombination codebook. In one embodiment, the Codebook-Config for Class AeMIMO-Type is fixed or pre-determined (hence, not configured). Forexample, Codebook-Config is fixed to 1. In another embodiment, theCodebook-Config for Class A eMIMO-Type is configured, where the set ofvalues of Codebook-Config include 1, 2, 3, and 4, which are identical toRel. 13 Class A codebook parameter. In yet another embodiment, arestricted subset of Codebook-Config parameter values is configurable,for example Codebook-Config=2, 3, and 4. In yet another embodiment, newCodebook-Config parameters (or beam groups) that are different from Rel.13 Class A codebook are defined for the hybrid configuration.

In general, the number and type (adjacent or orthogonal) of beamsreported in Class A eMIMO-Type by i₁ or (i_(1,1), i_(1,2)) depends onCodebook-Config parameter and W₁ codebook rank. For example, beams areadjacent for rank 1 W₁ codebook, and are orthogonal for rank 8 W₁codebook. Also, Codebook-Config 1 indicates 1 rank-1 beam andCodebook-Config 2, 3, 4 indicate 4 rank-1 beams. The reported beams(indicated by i₁ or (i_(1,1), i_(1,2))) are used by eNB to beam-formN_(P) ports associated with Class B eMIMO-Type. Depending on whether allor a subset of the reported beams are used by the eNB, there aremultiple possible hybrid configurations, the details of which areprovided later in the present disclosure.

In some embodiments, the hybrid configuration is fixed for each(Codebook-Config, N_(P)) configuration. So, no additional signalingabout hybrid configuration is required once (Codebook-Config, N_(P)) isconfigured.

In some embodiments, the UE is configured with one of multiple hybridconfigurations for each (Codebook-Config, N_(P)) configuration via RRCsignaling, where the set of possible configurable hybrid configurationscan be a subset of the set of all possible hybrid configurations.

In some embodiments of 0-a, only RI⁽¹⁾ is reported. Since RI⁽²⁾ is notreported in Class B eMIMO-Type, there are at least the followingalternatives for PMI and CQI reporting: the reported PMI and CQI inClass B eMIMO-Type correspond to the rank (r) which is equal to RI⁽¹⁾reported in Class A eMIMO-Type, i.e. r=RI⁽¹⁾; and the reported PMI andCQI in Class B eMIMO-Type correspond to the rank (r) which is smallerthan or equal to RI⁽¹⁾ reported in Class A eMIMO-Type, i.e. r≤RI⁽¹⁾,where r is either fixed (for example rank 1) or configured via RRCsignaling.

The set of possible values of RI⁽¹⁾ can either be {1, 2, . . . , 8}(i.e., 3-bit RI⁽¹⁾ indication) or a subset of {1, 2, . . . , 8}. In oneexample, the rank subset is {1, 2, 3, 4} (i.e., 2-bit RI⁽¹⁾ indication)or {1, 3, 5, 7} (i.e., 2-bit RI⁽¹⁾ indication) or {1, 2} (i.e., 1-bitRI⁽¹⁾ indication). In another example, for N_(P)=2, the rank subset is{1, 2}, for N_(P)=4, the rank subset is {1, 2, 3, 4}, and for N_(P)=8,the rank subset is {1, 2, . . . , 8}.

In some embodiments of 0-b, only RI⁽²⁾ is reported. Since RI⁽¹⁾ is notreported in Class A eMIMO-Type, there are at least the followingalternatives for i₁ or (i_(1,1), i_(1,2)) reporting: the reported i₁ or(i_(1,1), i_(1,2)) corresponds to (or is conditioned on) a fixed andpre-determined rank Class A W₁ codebook. For example, rank=1 or 8; therank on which i₁ or (i_(1,1), i_(1,2)) reporting is conditioned isconfigured via higher layer (RRC) signaling, where the set ofconfigurable rank is 1-8 (resulting in a 3-bit RRC parameter), or theset of configurable rank is a subset of 1-8. For example, {1, 3, 7} or{1, 3, 5, 7} (each resulting in a 2-bit RRC parameter); and the rank onwhich i₁ or (i_(1,1), i_(1,2)) reporting is conditioned depends on thenumber of ports (N_(P)) configured for the CSI-RS resource associatedwith Class B eMIMO-Type. For example: the rank for i₁ or (i_(1,1),i_(1,2)) reporting is 1 if N_(P)=2; the rank for i₁ or (i_(1,1),i_(1,2)) reporting is 3 if N_(P)=4; and the rank for i₁ or (i_(1,1),i_(1,2)) reporting is 7 if N_(P)=8.

FIG. 25 illustrates an example hybrid configuration forCodebook-Config=1 2500 according to embodiments of the presentdisclosure. An embodiment of the hybrid configuration forCodebook-Config=1 2500 shown in FIG. 25 is for illustration only. One ormore of the components illustrated in FIG. 25 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

TABLE 14 Class A (Codebook-Config = 1), Class B (N_(P) = 2, 4, 8), OnlyRI⁽²⁾ is reported Class A Class B, K = 1 Number of beams Class A Rank#RI Class B Configuration indicated by i₁ Beam types Codebook N_(P)RI⁽²⁾ bits Codebook 0 0-0 1 Single beam Rel. 13 (or 14) 2 1-2 1 Rel. 13Rank 1-2 (or 14) W₁ 1 1-0 2 2 orthogonal pairs Rel. 13 (or 14) 2 1-2 11-1 for 2D port layout; Rank 3-4 4 1-4 2 3 orthogonal pairs W₁ for 1Dport layout 2 2-0 4 4 orthogonal beams Rel. 13 (or 14) 2 1-2 1 2-1 Rank7-8 4 1-4 2 2-2 W₁ 8 1-8 3

If Codebook-Config=1, then the UE can be configured with one of thefollowing hybrid configurations. An illustration of the beams for theseconfigurations is shown in FIG. 25 , and the relevant details of theconfigurations are summarized in Table 14.

In some embodiments of configuration 0, the UE is configured with: Rel.13 (or extension in Rel. 14) Class A rank 1-2 W₁ codebook to derive i₁or (i_(1,1), i_(1,2)) indicating one beam; and the followingsub-configuration for Class B eMIMO-Type. In one embodiment ofconfiguration 0-0, Rel. 13 Class B, K=1 codebook for N_(P)=2 ports(which are beamformed using the beam indicated by i₁ or (i_(1,1),i_(1,2))), where the UE does not need to perform any beam selection andthe UE reports up to rank 2 PMI (i.e., 1-bit RI⁽²⁾) in Class BeMIMO-Type.

In some embodiments of configuration 1, the UE is configured with: Rel.13 (or extension in Rel. 14) Class A rank 3-4 W₁ codebook to derive i₁or (i_(1,1), i_(1,2)) indicating one of the two (three) orthogonal beampairs for 2D (1D) antenna port layouts, and one of the following twosub-configurations for Class B eMIMO-Type. In one embodiment ofconfiguration 1-0, Rel. 13 Class B, K=1 codebook for N_(P)=2 ports(which are beamformed using 1 out of 2 beams indicated by i₁ or(i_(1,1), i_(1,2))), where the UE does not need to perform any beamselection and the UE reports up to rank 2 PMI (i.e., 1-bit RI⁽²⁾) inClass B eMIMO-Type. In another embodiment of configuration 1-1, Rel. 13Class B, K=1 codebook for N_(P)=4 ports (which are beamformed using 2beams indicated by i₁ or (i_(1,1), i_(1,2))), where the UE performs 1out of 2 beam selection for rank 1-2, and selects both beams for rank3-4 and the UE reports up to rank 4 PMI (i.e., 2-bit RI⁽²⁾) in Class BeMIMO-Type.

In some embodiments of configuration 2, the UE is configured with: Rel.13 (or extension in Rel. 14) Class A rank 7-8 W₁ codebook to derive i₁or (i_(1,1), i_(1,2)) indicating four orthogonal beams, and one of thefollowing three sub-configurations for Class B eMIMO-Type. In oneembodiment of configuration 2-0, Rel. 13 Class B, K=1 codebook forN_(P)=2 ports (which are beamformed using 1 out of 4 orthogonal beamsindicated by i₁ or (i_(1,1), i_(1,2))), where the UE does not need toperform any beam selection and the UE reports up to rank 2 PMI (i.e.,1-bit RI⁽²⁾) in Class B eMIMO-Type. In another embodiment ofconfiguration 2-1, Rel. 13 Class B, K=1 codebook for N_(P)=4 ports(which are beamformed using 2 out of 4 orthogonal beams indicated by i₁or (i_(1,1), i_(1,2))), where the UE performs 1 out of 2 beam selectionfor rank 1-2, and selects both beams for rank 3-4 and the UE reports upto rank 4 PMI (i.e., 2-bit RI⁽²⁾) in Class B eMIMO-Type. In yet anotherembodiment of configuration 2-2, Rel. 13 Class B, K=1 codebook forN_(P)=8 ports (which are beamformed using 4 orthogonal beams indicatedby i₁ or (i_(1,1), i_(1,2))), where the UE performs 1 out 4 beamselection for rank 1-2, 2 out of 4 beam selection for rank 3-4, 3 out of4 beam selection for rank 5-6, and selects all 4 beams for rank 7-8 andthe UE reports up to rank 8 PMI (i.e., 3-bit RI⁽²⁾) in Class BeMIMO-Type.

FIG. 26 illustrates an example hybrid configuration forCodebook-Config=2, 3, and 4 2600 according to embodiments of the presentdisclosure. An embodiment of the hybrid configuration forCodebook-Config=2, 3, and 4 2600 shown in FIG. 26 is for illustrationonly. One or more of the components illustrated in FIG. 26 can beimplemented in specialized circuitry configured to perform the notedfunctions or one or more of the components can be implemented by one ormore processors executing instructions to perform the noted functions.Other embodiments are used without departing from the scope of thepresent disclosure.

TABLE 15 Class A (Codebook-Config = 2, 3, 4), Class B (N_(P) = 2, 4, 8),Only RI⁽²⁾ is reported Class A Class B, K = 1 Number of beams Class ARank #RI Class B Configuration indicated by i₁ Beam types Codebook N_(P)RI⁽²⁾ bits Codebook 0 0-0 4 4 closely Rel. 13 (or 14) 2 1-2 1 Rel. 13(or 14) 0-1 spaced beams Rank 1-2 4 0-2 W₁ 8 1 1-0 8 2 orthogonal groupsRel. 13 (or 14) 2 1-2 1 1-1 for 2D port layout; Rank 3-4 4 1-4 2 1-2 3orthogonal groups W₁ 8 for 1D port layout 2 2-0 4 4 orthogonal beamsRel. 13 (or 14) 2 1-2 1 2-1 Rank 7-8 4 1-4 2 2-2 W₁ 8 1-8 3

If Codebook-Config=2, 3, 4, then the UE is configured with one of thefollowing hybrid configurations. An illustration of the beams for thethree configurations is shown in FIG. 26 and the relevant details of theconfigurations are summarized in Table 15.

In some embodiments of configuration 0, the UE is configured with: Rel.13 (or extension in Rel. 14) Class A rank 1-2 W₁ codebook to derive i₁or (i_(1,1), i_(1,2)) indicating four beams; and one of the followingthree sub-configurations for Class B eMIMO-Type. In one example ofconfiguration 0-0, Rel. 13 Class B, K=1 codebook for N_(P)=2 ports(which are beamformed using 1 out of 4 beams indicated by i₁ or(i_(1,1), i_(1,2))), where the UE does not need to perform any beamselection and the UE reports up to rank 2 PMI (i.e., 1-bit RI⁽²⁾) inClass B eMIMO-Type. In another example of configuration 0-1, Rel. 13Class B, K=1 codebook for N_(P)=4 ports (which are beamformed using 2out of 4 beams indicated by i₁ or (i_(1,1), i_(1,2))), where the UEperforms 1 out of 2 beam selection and the UE reports up to rank 2 PMI(i.e., 1-bit RI⁽²⁾) in Class B eMIMO-Type. In yet another example ofconfiguration 0-2, Rel. 13 Class B, K=1 codebook for N_(P)=8 ports(which are beamformed using all 4 beams indicated by i₁ or (i_(1,1),i_(1,2))), where the UE performs 1 out of 4 beam selection and the UEreports up to rank 2 PMI (i.e., 1-bit RI⁽²⁾) in Class B eMIMO-Type.

In some embodiments of configuration 1, the UE is configured with: Rel.13 (or extension in Rel. 14) Class A rank 3-4 W₁ codebook to derive i₁or (i_(1,1), i_(1,2)) indicating one of the two (three) orthogonal beamgroups for 2D (1D) antenna port layouts where each orthogonal beam grouphas eight beams, four of which are located at location (0,0) and thereaming four are located at an orthogonal location, for example (O₁,0)or (0,O₂); and one of the following three sub-configurations for Class BeMIMO-Type. In one example of configuration 1-0, Rel. 13 Class B, K=1codebook for N_(P)=2 ports (which are beamformed using 1 out of 8 beamsindicated by i₁ or (i_(1,1), i_(1,2))), where the UE does not need toperform any beam selection and the UE reports up to rank 2 PMI (i.e.,1-bit RI⁽²⁾) in Class B eMIMO-Type. In another example of configuration1-1, Rel. 13 Class B, K=1 codebook for N_(P)=4 ports (which arebeamformed using 2 out of 8 beams indicated by i₁ or (i_(1,1),i_(1,2))), where the UE performs 1 out of 2 beam selection for rank 1-2,and selects both beams for rank 3-4 and the UE reports up to rank 4 PMI(i.e., 2-bit RI⁽²⁾) in Class B eMIMO-Type. In yet another example ofconfiguration 1-2: Rel. 13 Class B, K=1 codebook for N_(P)=8 ports(which are beamformed using 4 out of 8 beams indicated by i₁ or(i_(1,1), i_(1,2))), where the UE performs 1 out 4 beam selection forrank 1-2, and 2 out of 4 beam selection for rank 3-4 and the UE reportsup to rank 4 PMI (i.e., 2-bit RI⁽²⁾) in Class B eMIMO-Type.

In some embodiments of configuration 2, the UE is configured with: Rel.13 (or extension in Rel. 14) Class A rank 7-8 W₁ codebook to derive i₁or (i_(1,1), i_(1,2)) indicating four orthogonal beams; and one of thefollowing three sub-configurations. In one example of configuration 2-0,Rel. 13 Class B, K=1 codebook for N_(P)=2 ports (which are beamformedusing 1 out of 4 orthogonal beams indicated by i₁ or (i_(1,1),i_(1,2))), where the UE does not need to perform any beam selection andthe UE reports up to rank 2 PMI (i.e., 1-bit RI⁽²⁾) in Class BeMIMO-Type. In another example of configuration 2-1: Rel. 13 Class B,K=1 codebook for N_(P)=4 ports (which are beamformed using 2 out of 4orthogonal beams indicated by i₁ or (i_(1,1), i_(1,2))), where the UEperforms 1 out of 2 beam selection for rank 1-2, and selects both beamsfor rank 3-4 and the UE reports up to rank 4 PMI (i.e., 2-bit RI⁽²⁾) inClass B eMIMO-Type. In yet another example of configuration 2-2, Rel. 13Class B, K=1 codebook for N_(P)=8 ports (which are beamformed using 4orthogonal beams indicated by i₁ or (i_(1,1), i_(1,2))), where the UEperforms 1 out 4 beam selection for rank 1-2, 2 out of 4 beam selectionfor rank 3-4, 3 out of 4 beam selection for rank 5-6, and selects all 4beams for rank 7-8 and the UE reports up to rank 8 PMI (i.e., 3-bitRI⁽²⁾) in Class B eMIMO-Type.

The present disclosure covers the use of all the above configurations orsub-configurations. It also covers the use of only a subset of all theabove configurations or sub-configurations. If more than oneconfigurations or sub-configurations are used, the choice ofconfiguration or sub-configuration is performed via higher layersignaling.

For example, a subset of hybrid configurations or sub-configurations inTable 14 and Table 15 is used to configure one hybrid configuration tothe UE. An example of such a subset is shown in Table 16. The number ofconfigurations in Table 16 is 18. At least two possible configurationschemes can be used. First, a 5-bit RRC parameter can be used toconfigure a UE with one of the 18 hybrid configurations. Second, onlyone bit RRC parameter which configures a UE with one of the twoconfigurations in case of Codebook-Config 2, 3, 4 and N_(P)=4, 8. ThisRRC signaling is not needed if Codebook-Config=1 or (Codebook-Config 2,3, 4 and N_(P)=2). In this later configuration, Codebook-Config forClass A and the number of ports N_(P) for Class B are alreadyconfigurable via higher-layer signaling.

TABLE 16 Configurable hybrid configurations; Only RI⁽²⁾ is reportedClass A: Codebook-Config Class B: N_(P) Hybrid Configuration # RI⁽²⁾bits 1 2 0-0 (Table 14) 1 4 1-1 (Table 14) 2 8 2-2 (Table 14) 3 2, 3, or4 2 0-0 (Table 15) 1 4 0-1 (Table 15) 1 8 0-2 (Table 15) 1 4 1-1 (Table15) 2 8 2-2 (Table 15) 3

A variation of the above example where only one configuration issupported for Codebook-Config=2, 3, 4 and N_(P)=4, 8 can be described asfollows. Two examples are given in Table 17 and Table 18 below where thenumber of bits for RI⁽²⁾ is 1 and log₂(N_(P)), respectively. In thiscase, an additional RRC parameter is not needed.

TABLE 17 Configurable hybrid configurations; Only RI⁽²⁾ = 1 bit isreported Class A: Codebook- Config Class B: N_(P) Hybrid Configuration #RI⁽²⁾ bits 2, 3, or 4 2 0-0 (Table 15) 1 4 0-1 (Table 15) 1 8 0-2 (Table15) 1

TABLE 18 Configurable hybrid configurations; Only RI⁽²⁾ = log₂(N_(P))bits is reported Class A: Codebook-Config Class B: N_(P) HybridConfiguration # RI⁽²⁾ bits 2, 3, or 4 2 0-0 (Table 15) 1 4 1-1 (Table15) 2 8 2-2 (Table 15) 3

In some embodiments of 0-c, both RI⁽¹⁾ and RI⁽²⁾ are reported. SinceRI⁽¹⁾ is reported in Class A eMIMO-Type, there are at least thefollowing alternatives for i₁ or (i_(1,1), i_(1,2)) reporting: thereported i₁ or (i_(1,1), i_(1,2)) corresponds to (or is conditioned on)any of rank 1-8 Class A W₁ codebooks, i.e. RI⁽¹⁾=1, 2, . . . , 8 (i.e.,3-bit RI⁽¹⁾); the reported i₁ or (i_(1,1), i_(1,2)) is conditioned on asubset of all rank 1-8 Class A W₁ codebooks, where the subset is eitherpre-determined or RRC configured, where, for example, RI⁽¹⁾=1, 3 (i.e.,1-bit RI⁽¹⁾), RI⁽¹⁾=1, 3, 5 (i.e., 2-bit RI⁽¹⁾), or RI⁽¹⁾=1, 3, 5, 7(i.e., 2-bit RI⁽¹⁾); and the rank on which i₁ or (i_(1,1), i_(1,2))reporting is conditioned depends on the number of ports (N_(P))configured for the CSI0RS resource associated with Class B eMIMO-Type,where, for example, RI⁽¹⁾=1 (so, no RI⁽¹⁾ indication is needed) ifN_(P)=2, RI⁽¹⁾=1, 3 (i.e., 1-bit RI⁽¹⁾) if N_(P)=4; or RI⁽¹⁾=1, 3, 5, 7(i.e., 2-bit RI⁽¹⁾) if N_(P)=8.

Also, since RI is reported in both eMIMO-Types (associated with the twoconfigured NZP CSI-RS resources), there can be following two cases: Case0: RI⁽¹⁾ and RI⁽²⁾ are dependent. For example, RI⁽²⁾ reporting is only1-bit for N_(P)=2, 4, 8, where one possible embodiment for this is toutilize rank inheritance feature in Rel. 12. That is, a RI referenceresource for the second eMIMO-Type is defined to as the resourceassociated with the first eMIMO-Type; and Case 1: RI⁽¹⁾ and RI⁽²⁾ areindependent. In particular, RI⁽²⁾ reporting is 1, 2, and 3 bits forN_(P)=2, 4, and 8, respectively, in this instance, CQI and PMIassociated with the second eMIMO-Type (of Class B) are calculatedconditioned on the reported RI⁽²⁾. For periodic PUCCH-based CSIreporting, the reported RI⁽²⁾ is the last reported periodic RI⁽²⁾.

One of the above two cases can be configured to a UE via RRC signaling.Alternatively, the case is pre-determined, for example Case 0.

Similar to the aforementioned embodiments of 0-b, if Codebook-Config=1,then the UE can be configured with one of the several hybridconfigurations (or sub-configurations). Example configurations aresummarized in Table 19 and Table 20, respectively, for Case 0 and Case 1of rank reporting and N_(P)=2, 4, 8.

TABLE 19 Class A (Codebook-Config = 1) and Class B (N_(P) = 2, 4, 8),both RI⁽¹⁾ and RI⁽²⁾ are report, Case 0: RI⁽¹⁾ and RI⁽²⁾ are dependentClass A Class B, K = 1 #RI Rank Number of beams Class A Rank #RI Class BConfig. bits RI⁽¹⁾ indicated by i₁ Beam types Codebook N_(P) RI⁽²⁾ bitsCodebook 0 2 1-2 1 — Rel. 13 (or 14) 2 1-2 1 Rel. 13 (or 14) Rank 1-2 W₁1 3-4 2 2 orthogonal pairs Rel. 13 (or 14) 4 3-4 for 2D port layout;Rank 3-4 3 orthogonal pairs W₁ for 1D port layout 2 5-6 3 3 orthogonalbeams Rel. 13 (or 14) 8 5-6 Rank 5-6 W₁ 3 7-8 4 4 orthogonal beams Rel.13 (or 14) 8 7-8 Rank 7-8 W₁

TABLE 20 Class A (Codebook-Config = 1) and Class B (N_(P) = 2, 4, 8),both RI⁽¹⁾ and RI⁽²⁾ are report, Case 1: RI⁽¹⁾ and RI⁽²⁾ are independentClass A Class B, K = 1 #RI Rank Number of beams Class A Rank #RI Class BConfig. bits RI⁽¹⁾ indicated by i₁ Beam types Codebook N_(P) R⁽²⁾ bitsCodebook 0 0-0 2 1-2 1 — Rel. 13 (or 14) 2 1-2 1 Rel. 13 (or 14) Rank1-2 W₁ 1 1-0 3-4 2 2 orthogonal pairs Rel. 13 (or 14) 2 1-2 1 1-1 for 2Dport layout; Rank 3-4 4 1-4 2 3 orthogonal pairs W₁ for 1D port layout 22-0 5-6 3 3 orthogonal beams Rel. 13 (or 14) 2 1-2 1 2-1 Rank 7-8 4 1-42 2-2 W₁ 8 1-6 3 3 3-0 7-8 4 4 orthogonal beams Rel. 13 (or 14) 2 1-2 13-1 Rank 7-8 4 1-4 2 3-2 W₁ 8 1-8 3

Another example configurations are summarized in Table 21 and Table 22for Case 0 and Case 1 of rank reporting, and N_(P)=2, 4, 6, 8. Note thatin this case, a new Class B codebook for N_(P)=6 needs to be configured.

TABLE 21 Class A (Codebook-Config = 1) and Class B (N_(P) = 2, 4, 6, 8),both RI⁽¹⁾ and RI⁽²⁾ are report, Case 0: RI⁽¹⁾ and RI⁽²⁾ are dependentClass A Class B, K = 1 #RI Rank Number of beams Class A Rank #RI Class BConfig. bits RI⁽¹⁾ indicated by i₁ Beam types Codebook N_(P) RI⁽²⁾ bitsCodebook 0 2 1-2 1 — Rel. 13 (or 14) 2 1-2 1 Rel. 13 (or 14) Rank 1-2 W₁1 3-4 2 2 orthogonal pairs Rel. 13 (or 14) 4 3-4 for 2D port layout;Rank 3-4 3 orthogonal pairs W₁ for 1D port layout 2 5-6 3 3 orthogonalbeams Rel. 13 (or 14) 6 5-6 Rank 5-6 W₁ 3 7-8 4 4 orthogonal beams Rel.13 (or 14) 8 7-8 Rank 7-8 W₁

TABLE 22 Class A (Codebook-Config = 1) and Class B (N_(P) = 2, 4, 6, 8),both RI⁽¹⁾ and RI⁽²⁾ are report, Case 1: RI⁽¹⁾ and RI⁽²⁾ are independentClass A Class B, K = 1 #RI Rank Number of beams Class A Rank #RI Class BConfig. bits RI⁽¹⁾ indicated by i₁ Beam types Codebook N_(P) RI⁽²⁾ bitsCodebook 0 0-0 2 1-2 1 — Rel. 13 (or 14) 2 1-2 1 Rel. 13 (or 14) Rank1-2 W₁ 1 1-0 3-4 2 2 orthogonal pairs Rel. 13 (or 14) 2 1-2 1 1-1 for 2Dport layout; Rank 3-4 4 1-4 2 3 orthogonal pairs W₁ for 1D port layout 22-0 5-6 3 3 orthogonal beams Rel. 13 (or 14) 2 1-2 1 2-1 Rank 5-6 4 1-42 2-2 W₁ 6 1-6 3 3 3-0 7-8 4 4 orthogonal beams Rel. 13 (or 14) 2 1-2 13-1 Rank 7-8 4 1-4 2 3-2 W₁ 6 1-6 3 3-3 8 1-8 3

If Codebook-Config=2, 3, 4, then the hybrid eMIMO-Type configurationscan be formulated similarly. Example configurations are summarized inTable 23 and Table 24, respectively, for Case 0 and Case 1 of rankreporting and N_(P)=2, 4, 8.

TABLE 23 Class A (Codebook-Config = 2, 3, 4) and Class B (N_(P) = 2, 4,8), both RI⁽¹⁾ and RI⁽²⁾ are report, Case 0: RI⁽¹⁾ and RI⁽²⁾ aredependent Class A Class B, K = 1 #RI Rank Number of beams Class A Rank#RI Class B Config. bits RI⁽¹⁾ indicated by i₁ Beam types Codebook N_(P)RI⁽²⁾ bits Codebook 0 0-0 2 1-2 4 — Rel. 13 (or 14) 2 1-2 1 Rel. 13 (or14) 0-1 Rank 1-2 4 0-2 W₁ 8 1 1-1 3-4 8 2 orthogonal pairs Rel. 13 (or14) 4 3-4 1-2 for 2D port layout; Rank 3-4 8 3 orthogonal pairs W₁ for1D port layout 2 2-2 5-6 3 3 orthogonal beams Rel. 13 (or 14) 8 5-6 Rank5-6 W₁ 3 3-2 7-8 4 4 orthogonal beams Rel. 13 (or 14) 8 7-8 Rank 7-8 W₁

TABLE 24 Class A (Codebook-Config = 2, 3, 4) and Class B (N_(P) = 2, 4,8), both RI⁽¹⁾ and RI⁽²⁾ are report, Case 1: RI⁽¹⁾ and RI⁽²⁾ areindependent Class A Class B, K = 1 #RI Rank Number of beams Class A Rank#RI Class B Config. bits RI⁽¹⁾ indicated by i₁ Beam types Codebook N_(P)RI⁽²⁾ bits Codebook 0 0-0 2 1-2 4 — Rel. 13 (or 14) 2 1-2 1 Rel. 13 (or14) 0-1 Rank 1-2 4 0-2 W₁ 8 1 1-0 3-4 8 2 orthogonal pairs Rel. 13 (or14) 2 1-2 1 1-1 for 2D port layout; Rank 3-4 4 1-4 2 1-2 3 orthogonalpairs W₁ 8 for 1D port layout 2 2-0 5-6 3 3 orthogonal beams Rel. 13 (or14) 2 1-2 1 2-1 Rank 7-8 4 1-4 2 2-2 W₁ 8 1-6 3 3-0 7-8 4 4 orthogonalbeams Rel. 13 (or 14) 2 1-2 1 3-1 Rank 7-8 4 1-4 2 3-2 W₁ 8 1-8 3

The present disclosure covers the use of all the above configurations orsub-configurations. It also covers the use of only a subset of all theabove configurations or sub-configurations. If more than oneconfigurations or sub-configurations are used, the choice ofconfiguration or sub-configuration is performed via higher layersignaling.

For example, a subset of hybrid configurations or sub-configurations inTable 19, Table 20, Table 23, and Table 24 is used to configure onehybrid configuration to the UE. An example of such a subset is shown inTable 25. In this subset, RI⁽¹⁾=2 bits corresponds to rank 1-2, rank3-4, rank 5-6, and rank 7-8 Class A W₁ codebooks. The total number ofconfigurations in the Table is 32. At least two possible configurationschemes can be used. First, a 5-bit RRC parameter can be used toconfigure a UE with one of the 32 hybrid configurations. Second, onlyone bit RRC parameter which configures a UE for either Case 0 (RI⁽¹⁾ andRI⁽²⁾ calculation are dependent) or Case 1 (RI⁽¹⁾ and RI⁽²⁾ calculationare independent) is used. Since Codebook-Config for Class A and thenumber of ports N_(P) for Class B are already configurable viahigher-layer signaling, the choice of hybrid configuration for a givencombination of Codebook-Config for Class A and the number of ports N_(P)for Class B, along with the sets of possible values for RI⁽¹⁾ and RI⁽²⁾,are fixed.

TABLE 25 Configurable hybrid configurations; both RI⁽¹⁾ and RI⁽²⁾ arereported Class A: Codebook- Class Hybrid # RI⁽¹⁾ # RI⁽²⁾ Case Config B:N_(P) Configuration bits bits 0: RI⁽¹⁾ and 1 2 0 (Table 18) 2 1 RI⁽²⁾calculation 4 1 (Table 18) are dependent 8 2 (Table 18) 8 3 (Table 18)2, 3, or 4 2 0-0 (Table 23) 2 1 4 1-1 (Table 23) 8 2-2 (Table 23) 8 2-3(Table 23) 1: RI⁽¹⁾ and 1 2 0-0 (Table 20) 2 1 RI⁽²⁾ calculation 4 1-1(Table 20) 2 are independent 8 2-2 (Table 20) 3 8 3-2 (Table 20) 3 2, 3,or 4 2 0-0 (Table 24) 2 1 4 1-1 (Table 24) 2 8 2-2 (Table 24) 3 8 3-2(Table 24) 3

Another example of the subset with only one hybrid configuration(instead of two) for N_(P)=8 is shown in Table 26. In this subset,RI⁽¹⁾=2 bits corresponds to rank 1-2, rank 3-4, and rank 7-8 Class A W₁codebooks.

TABLE 26 Configurable hybrid configurations; both RI⁽¹⁾ and RI⁽²⁾ arereported Class A: Codebook- Class Hybrid # RI⁽¹⁾ # RI⁽²⁾ Case Config B:N_(P) Configuration bits bits 0: RI⁽¹⁾ and 1 2 0 (Table 19) 2 1 RI⁽²⁾ 41 (Table 19) calculation are 8 3 (Table 19) dependent 2, 3, or 4 2 0-0(Table 23) 2 1 4 1-1 (Table 23) 8 2-3 (Table 23) 1: RI⁽¹⁾ and 1 2 0-0(Table 20) 2 1 RI⁽²⁾ 4 1-1 (Table 20) 2 calculation are 8 3-2 (Table 20)3 independent 2, 3, or 4 2 0-0 (Table 24) 2 1 4 1-1 (Table 24) 2 8 3-2(Table 24) 3

A variation of the above example where only independent RI⁽¹⁾ and RI⁽²⁾calculation is supported can be described as follows. Two examples aregiven in Table 27 and Table 28 below where the number of bits for RI⁽¹⁾is 2 and 1, respectively. In this case, an additional RRC parameter isnot needed. In Table 27, RI⁽¹⁾=2 bits corresponds to rank 1-2, rank 3-4,and rank 7-8 Class A W₁ codebooks. In Table 28, RI⁽¹⁾=1 bit correspondsto rank 1-2 and rank 7-8 Class A W₁ codebooks.

TABLE 27 Configurable hybrid configurations; both RI⁽¹⁾ (2 bits) andRI⁽²⁾ are reported Class A: Codebook- Class Hybrid Config B: N_(P)Configuration # RI⁽¹⁾ bits # RI⁽²⁾ bits 1 2 0-0 (Table 20) 2 1 4 1-1(Table 20) 2 8 3-2 (Table 20) 3 2, 3, or 4 2 0-0 (Table 24) 2 1 4 1-1(Table 24) 2 8 3-2 (Table 24) 3

TABLE 28 Configurable hybrid configurations; both RI⁽¹⁾ (1 bit) andRI⁽²⁾ are reported Class A: Codebook- Hybrid Config Class B: N_(P)Configuration # RI⁽¹⁾ bits # RI⁽²⁾ bits 1 2 0-0 (Table 20) 1 1 4 3-1(Table 20) 2 8 3-2 (Table 20) 3 2, 3, or 4 2 0-0 (Table 24) 1 1 4 3-1(Table 24) 2 8 3-2 (Table 24) 3

A few other examples of RI⁽¹⁾ and RI⁽²⁾ reporting are shown in Table 29,Table 20, Table 31, and Table 32, where: the number of bits for RI⁽¹⁾=0for N_(p)=2 Class B ports (i.e., RI⁽¹⁾ is not reported); and the numberof bits for RI⁽¹⁾≠0 for N_(p)=4 and 8 Class B ports.

In the example in Table 29, RI⁽¹⁾=log₂(N_(P)/2) bits andRI⁽²⁾=log₂(N_(P)) bits. The reported RI⁽¹⁾ indicates a Class A codebookrank as follows: 0-bit RI⁽¹⁾ indicates rank 1 for N_(p)=2 (i.e., RI⁽¹⁾is not reported); 1-bit RI⁽¹⁾ indicates rank 1 or 3 for N_(p)=4; and2-bit RI⁽¹⁾ indicates rank 1, 3, 5, or 7 for N_(p)=8. The reported RI⁽²⁾indicates a Class B codebook rank 1, 2, . . . , or N_(p).

In the example in Table 30, RI⁽¹⁾=0 or 1 bit and RI⁽²⁾=log₂(N_(P)) bits.The reported RI⁽¹⁾ indicates a Class A codebook rank as follows: 0-bitRI⁽¹⁾ indicates rank 1 for N_(p)=2 (i.e., RI⁽¹⁾ is not reported); 1-bitRI⁽¹⁾ indicates rank 1 or 3 for N_(p)=4; and 1-bit RI⁽¹⁾ indicates rankeither (Alt 0) 1 or 3, or (Alt 1) 1 or 7 for N_(p)=8. The reported RI⁽²⁾indicates a Class B codebook rank 1, 2, . . . , or N_(p).

In the example in Table 31, RI⁽¹⁾=log₂(N_(P)/2) bits and RI⁽²⁾=1 bit.The reported RI⁽¹⁾ indicates a Class A codebook rank as follows: 0-bitRI⁽¹⁾ indicates rank 1 for N_(p)=2 (i.e., RI⁽¹⁾ is not reported); 1-bitRI⁽¹⁾ indicates rank 1 or 3 for N_(p)=4; and 2-bit RI⁽¹⁾ indicates rank1, 3, 5, or 7 for N_(p)=8. The reported 1-bit RI⁽²⁾ indicates a Class Bcodebook rank which depends on the reported RI⁽¹⁾. In one example, 1-bitRI⁽²⁾ indicates rank 1 or 2 for N_(p)=2. In another example, forN_(p)=4, 1-bit RI⁽²⁾ indicates: rank 1 or 2 if RI⁽¹⁾ indicates rank 1;and rank 3 or 4 if RI⁽¹⁾ indicates rank 3. In yet another example, forN_(p)=8, 1-bit RI⁽²⁾ indicates: rank 1 or 2 if RI⁽¹⁾ indicates rank 1;rank 3 or 4 if RI⁽¹⁾ indicates rank 3; rank 5 or 6 if RI⁽¹⁾ indicatesrank 5; and rank 7 or 8 if RI⁽¹⁾ indicates rank 7.

In the example in Table 32, RI⁽¹⁾=log₂(N_(P)/2) bits and RI⁽²⁾=1 or 3bits. The reported RI⁽¹⁾ indicates a Class A codebook rank as follows:0-bit RI⁽¹⁾ indicates rank 1 for N_(p)=2 (i.e., RI⁽¹⁾ is not reported);1-bit RI⁽¹⁾ indicates rank 1 or 3 for N_(p)=4; and 2-bit RI⁽¹⁾ indicatesrank 1, 3, 5, or 7 for N_(p)=8. The reported 1-bit RI⁽²⁾ indicates aClass B codebook rank which depends on the reported RI⁽¹⁾. In oneexample, 1-bit RI⁽²⁾ indicates rank 1 or 2 for N_(p)=2. In anotherexample, for N_(p)=4, 1-bit RI⁽²⁾ indicates: rank 1 or 2 if RI⁽¹⁾indicates rank 1; and rank 3 or 4 if RI⁽¹⁾ indicates rank 3. In yetanother example, for N_(p)=8, 3-bit RI⁽²⁾ indicates rank 1-8.

TABLE 29 Configurable hybrid configurations; RI⁽¹⁾ = log₂(N_(P)/2) bitand RI₍₂₎ = log₂(N_(P)) bit Class A: Codebook- # RI⁽¹⁾ Class A # RI⁽²⁾Config Class B: N_(P) bits codebook rank bits 1, 2, 3 or 4 2 0 1 1 4 11, 3 2 8 2 1, 3, 5, 7 3

TABLE 30 Configurable hybrid configurations; both RI⁽¹⁾ = 0 or 1 bit andRI⁽²⁾ = log₂(N_(P)) bit Class A: Codebook- Alt 0: Class A Config ClassB: N_(P) # RI⁽¹⁾ bits codebook rank # RI⁽²⁾ bits 1, 2, 3 or 4 2 0 1 1 41 1, 3 2 8 1 1, 3 3 Class A: Alt 1: Class A Codebook- codebook ConfigClass B: N_(P) # RI⁽¹⁾ bits rank # RI⁽²⁾ bits 1, 2, 3 or 4 2 0 1 1 4 11, 3 2 8 1 1, 7 3

TABLE 31 Configurable hybrid configurations; RI⁽¹⁾ = log₂(N_(P)/2) bitand RI⁽²⁾ = 1 bit Class A: Codebook- Class A Config Class B: N_(P) #RI⁽¹⁾ bits codebook rank # RI⁽²⁾ bits 1, 2, 3 or 4 2 0 1 1 4 1 1, 3 1 82 1, 3, 5, 7 1

TABLE 32 Configurable hybrid configurations; RI⁽¹⁾ = log₂(N_(P)/2) bitand RI⁽²⁾ = 1 or 3 bit Class A: Codebook- Alt 0: Class A Config Class B:N_(P) # RI⁽¹⁾ bits codebook rank # RI⁽²⁾ bits 1, 2, 3 or 4 2 0 1 1 4 11, 3 1 8 2 1, 3, 5, 7 3

In some embodiments, a UE is configured with hybrid configuration 0-c inTable 13 with reporting content: for the 1^(st) eMIMO-Type (CLASS A),i1⁽¹⁾ and x-bit RI⁽¹⁾ are reported, while CQI⁽¹⁾ and i2⁽¹⁾ are notreported, where if UE supports up to 2 layers, x=0, if UE supports up to4 layer, x=1 where RI⁽¹⁾={1, 3}, or if UE supports up to 8 layer, x=2where RI⁽¹⁾={1, 3, 5, 7}; and for the 2^(nd) eMIMO-Type (CLASS B K=1),CQI⁽²⁾, PMI⁽²⁾, RI⁽²⁾ are reported. Note superscript (y) represents they-th eMIMO-Type, where y=1, 2.

In some embodiments, a UE is configured with hybrid configuration 0-c inTable 13 with no inter-dependence between CSI calculations across twoeMIMO-Types.

In some embodiments, a UE is configured with hybrid configuration 0-c inTable 13 with rank indication according to one of Table 33 to Table 37,where the Tables show the fields and the corresponding bit width for therank indication feedback for PDSCH transmissions associated withtransmission mode 3, transmission mode 4, transmission mode 8 configuredwith PMI/RI reporting, transmission mode 9 configured with PMI/RIreporting with 2/4/8 antenna ports, transmission mode 10 configured withPMI/RI reporting with 2/4/8 antenna ports, and transmission mode 9/10configured with PMI/RI reporting with 2/4/8 antenna ports and higherlayer parameter eMIMO-Type, and eMIMO-Type is set to ‘CLASS B’ with K=1,transmission mode 9/10 configured with PMI/RI reporting with 8/12/16antenna ports and higher layer parameter eMIMO-Type, and eMIMO-Type isset to ‘CLASS A’, and transmission mode 9/10 configured without PMIreporting and higher layer parameter eMIMO-Type, and eMIMO-Type is setto ‘CLASS B’ with K=1 with 2/4/8 antenna ports.

TABLE 33 Fields for rank indication feedback Bit width8/12/16/20/24/28/32 2 4 antenna ports antenna ports antenna Max 1 or Max4 Max 1 or Max 4 Max 8 Field ports 2 layers layers 2 layers layerslayers Rank 1 1 2 1 2 3 indication Rank {1, 2} {1, 2} {1, 2, {1, 2} {1,2, {1, 2, 3, 4} 3, 4} 3, 4, 5, 6, 7, 8}

TABLE 34 Fields for rank indication feedback Bit width8/12/16/20/24/28/32 2 4 antenna ports antenna ports antenna Max 1 or Max4 Max 1 or Max 4 Max 8 Field ports 2 layers layers 2 layers layerslayers Rank 0 0 1 0 1 2 indication Rank {1} {1} {1, 3} {1} {1, 3} {1, 3,5, 7}

TABLE 35 Fields for rank indication feedback Bit width8/12/16/20/24/28/32 2 4 antenna ports antenna ports antenna Max 1 or Max4 Max 1 or Max 4 Max 8 Field ports 2 layers layers 2 layers layerslayers Rank 0 0 1 0 1 1 indication Rank {1} {1} {1, 3} {1} {1, 3} {1, 3}

TABLE 36 Fields for rank indication feedback Bit width8/12/16/20/24/28/32 2 4 antenna ports antenna ports antenna Max 1 or Max4 Max 1 or Max 4 Max 8 Field ports 2 layers layers 2 layers layerslayers Rank 0 0 1 0 1 1 indication Rank {1} {1} {1, 3} {1} {1, 3} {1, 7}

TABLE 37 Fields for rank indication feedback Bit width8/12/16/20/24/28/32 2 4 antenna ports antenna ports antenna Max 1 or Max4 Max 1 or Max 4 Max 8 Field ports 2 layers layers 2 layers layerslayers Rank 0 0 2 0 2 2 indication Rank {1} {1} {1, 2, {1} {1, 2, {1, 3,3, 4} 3, 4} 5, 7}

In some embodiments, a UE is configured with a hybrid CSI reporting inwhich the 1st eMIMO-Type is Class B, K₁>1 and the 2nd eMIMO-Type isClass B, K₂=1. The CSI reported in the first Class B eMIMO-Type iseither: alternative 2-a (Table 13): CRI and associated PMI (and RI⁽¹⁾);or alternative 2-b (Table 13): PMI (and RI(1), if applicable) for eachCSI-RS resource, and that reported in the 2nd Class B eMIMO-Typeincludes RI⁽²⁾, CQI, and PMI.

In one example of embodiment 2-b, the 1st eMIMO-Type is associated withK₁=2 CSI-RS resources. An exemplary use case is to implement theso-called partial-port (non-precoded) CSI-RS where the K₁=2 CSI-RSresources are used to represent the two dimensions of two-dimensionalantenna port layouts (FIG. 12 and FIG. 13 ).

Note that for the special case of one-dimensional (1D) antenna portlayouts, only one dimension is present. Therefore, the 1st eMIMO-Type isassociated with K₁=1 CSI-RS resource. With K₁=2 CSI-RS resources, thefirst of the two CSI-RS resources can be associated with the 1st antennaport dimension and the second of the two CSI-RS resources can beassociated with the 2nd antenna port dimension. For instance, the firstof the two CSI-RS resources can be associated with one of the rows (e.g.row 1) of antenna ports and the second of the two CSI-RS resources canbe associated with one of the columns (e.g. column 1) of antenna ports.The 2nd CSI-RS resource is BF using the two reported PMIs in the 1steMIMO-Type.

FIG. 27 illustrates an example hybrid CSI reporting 2700 according toembodiments of the present disclosure. An embodiment of the hybrid CSIreporting 2700 shown in FIG. 27 is for illustration only. One or more ofthe components illustrated in FIG. 27 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

An example of this scheme is shown in FIG. 27 . As shown in FIG. 27 ,the first CSI-RS corresponds to “Class B K₁=2 eMIMO-Type” in which NPCSI-RS is transmitted from a subset (one row or one column) of antennaports. There are two CSI-RS resources: first CSI-RS 1 is for the row andfirst CSI-RS 2 is for the column. The second CSI-RS corresponds to“Class B K₂=1 eMIMO-Type” in which BF CSI-RS is transmitted from twobeam-formed ports which are beam-formed using the beams associated withthe first PMI. The UE derives: 1st CSI: i_(1,1) of the first PMI pair(i_(1,1), i_(1,2)) using the NP CSI-RS corresponding to the row and a 16port codebook, and i_(1,2) of the first PMI pair (i_(1,1), i_(1,2))using the NP CSI-RS corresponding to the column and a 4 port codebook;and 2nd CSI: the second PMI i₂, CQI and RI using BF CSI-RS and a 2 portcodebook.

TABLE 38 Codebook alternatives for 1st Class B eMIMO-Type in alternative2-b (Table 13) Codebook 1st dimension 2nd dimension Type codebookcodebook 0 Co-pol Co-pol 1 Co-pol Dual-pol 2 Dual-pol Co-pol 3 Dual-polDual-pol

FIG. 28 illustrates an example codebook types for Class B K₁=2eMIMO-Type 2800 according to embodiments of the present disclosure. Anembodiment of the codebook types for Class B K₁=2 eMIMO-Type 2800 shownin FIG. 28 is for illustration only. One or more of the componentsillustrated in FIG. 28 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, the codebook for the 1st Class B K₁=2 eMIMO-Type isone of the four types as tabulated in Table 38 and shown in FIG. 28 ,where there are two types of codebooks for the two dimensions. In oneexample, the co-pol codebook is used for PMI calculation if the CSI-RSis transmitted from the antenna ports with one polarization only (e.g.+45 or −45). In another example, the dual-pol codebook is used for PMIcalculation if the CSI-RS is transmitted from the antenna ports withboth polarizations. Examples of dual-pol codebooks include Rel. 10 8-Tx,Rel. 12 4-Tx, and Rel. 13 Class A codebooks.

An example of the 1st eMIMO-Type codebook for different antenna portlayouts shown in FIG. 12 and FIG. 13 is shown in Table 39. In thistable, codebook types 1 and 2 (Table 38) is assumed, i.e. the co-polcodebook is configured in one of the two dimensions, and the otherdimension is configured with a dual-pol (legacy) codebook. The othercombinations of the 1st eMIMO-Type codebook can be constructedsimilarly.

TABLE 39 1st eMIMO-Type codebook for 1st and 2nd dimensions Number ofCSI- RS 1st eMIMO-Type Codebook antenna (N₁, 1st (N₂, 2nd ports, P (N₁,N₂) P₁) dimension P₂) dimension 8 (2, 2) (2, 2) Rel. 12 4-Tx W1 (2, 1)Co-pol 2-Tx 12 (2, 3) (2, 2) Rel. 12 4-Tx W1 (3, 1) Co-pol 3-Tx (3, 2)(3, 1) Co-pol 3-Tx (2, 2) Rel. 12 4-Tx W1 16 (2, 4) (2, 1) Co-pol 2-Tx(4, 2) Rel. 10 8-Tx W1 (4, 2) (4, 2) Rel. 10 8-Tx W1 (2, 1) Co-pol 2-Tx(8, 1) (8, 1) Co-pol 8-Tx — — 20 (1, — — (10, Co-pol 10-Tx 10) 1) (2, 5)(2, 2) Rel. 12 4-Tx W1 (5, 1) Co-pol 5-Tx (5, 2) (5, 1) Co-pol 5-Tx (2,2) Rel. 12 4-Tx W1 (10, 1)  (10, 1)  Co-pol 10-Tx — — 24 (1, 12) — —(12, Co-pol 12-Tx 1) (2, 6) (2, 2) Rel. 12 4-Tx W1 (6, 1) Co-pol 6-Tx(3, 4) (3, 1) Co-pol 3-Tx (4, 2) Rel. 10 8-Tx W1 (4, 3) (4, 2) Rel. 108-Tx W1 (3, 1) Co-pol 3-Tx (6, 2) (6, 1) Co-pol 6-Tx (2, 2) Rel. 12 4-TxW1 (12, 1)  (12, 1)  Co-pol 12-Tx — — 28 (1, — — (14, Co-pol 14-Tx14) 1) (2, 7) (2, 2) Rel. 12 4-Tx W1 (7, 1) Co-pol 7-Tx (7, 2) (7, 1)Co-pol 7-Tx (2, 2) Rel. 12 4-Tx W1  (14, 1) (14, 1)  Co-pol 14-Tx — — 32(1, — — (16, Co-pol 16-Tx 16) 1) (2, 8) (2, 1) Co-pol 2-Tx (8, 2) Rel.13 16-Tx W1 (4, 4) (4, 2) Rel. 10 8-Tx W1 (4, 1) Co-pol 4-Tx (8, 2) (8,2) Rel. 13 16-Tx (2, 1) Co-pol 2-Tx W1 (16, 1)  (16, 1)  Co-pol 16-Tx ——

In one example of 1, the co-pol codebook is rank 1 and the correspondingPMI indicates a single beam. An example of such a codebook is shown inTable 40, where the dimension d=1, 2, and

$u_{m_{d}} = {\begin{bmatrix}1 & e^{j\frac{2\pi m_{d}}{O_{d}N_{d}}} & \ldots & e^{j\frac{2\pi{m_{d}({N_{d} - 1})}}{O_{d}N_{d}}}\end{bmatrix}^{T}.}$

TABLE 40 W₁ Co-pol Codebook for 1-layer CSI reporting using antennaports 15 to 14 + P m_(d) Precoder 0, 1, . . . , O_(d)N_(d) − 1$W_{m_{d}}^{(1)} = \frac{u_{m_{d}}}{\sqrt{N_{d}}}$

The overall rank of the 1st eMIMO-Type depends on the co-pol codebooktype (Table 39): for Codebook Type=0, the overall rank is 1. So, RI⁽¹⁾is not reported; and for Codebook Type=1, 2, the overall rank can be >1if rank >1 is reported from the dimension associated with the dual-polcodebook.

In another example of 2, the co-pol codebook is rank >1 and thecorresponding PMI indicates orthogonal beams. An example of rank-2co-pol codebook is shown in Table 41, where the dimension d=1, 2.

TABLE 41 W₁ Co-pol Codebook for 2-layer CSI reporting using antennaports 15 to 14 + P N₁, N₂ > 1 m_(d) Precoder 0, 1, . . . , O_(d)N_(d) −1$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{m_{d}}\ u_{m_{d} + O_{d}}} \right\rbrack}$N₁ or N₂ = 1 m_(d) Precoder 0, 1, . . . , O_(d)N_(d) − 1$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{m_{d}}\ u_{m_{d} + O_{d}}} \right\rbrack}$O_(d)N_(d), O_(d)N_(d) + 1, . . . , 2O_(d)N_(d) − 1$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{m_{d}}u_{m_{d} + {2O_{d}}}} \right\rbrack}$2O_(d)N_(d), O_(d)N_(d) + 1, . . . , 3O_(d)N_(d) − 1$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{m_{d}}u_{m_{d} + {3O_{d}}}} \right\rbrack}$

In yet another example of 3, the co-pol codebook is rank 1 and thecorresponding PMI indicates a group of beams. An example of such acodebook is shown in Table 42 where the dimension d=1, 2, and the typeof beam group is indicated by the higher layer RRC parameterCodebook-Config.

TABLE 42 W₁ Co-pol Codebook for 1-layer CSI reporting using antennaports 15 to 14 + P Value of Codebook-Config m_(d) Precoder 1 0, 1, . . ., O_(d)N_(d) − 1 $W_{m_{d}}^{(1)} = \frac{u_{m_{d}}}{\sqrt{N_{d}}}$ 2${0,1,_{}\ldots,\frac{O_{d}N_{d}}{2}} - 1$$W_{m_{d}}^{(1)} = {\frac{1}{\sqrt{N_{d}}}\left\lbrack {u_{2m_{d}}\ u_{{2m_{d}} + 1}} \right\rbrack}$3 ${0,1,_{}\ldots,\frac{O_{d}N_{d}}{2}} - 1$${W_{m_{d}}^{(1)} = {\frac{1}{\sqrt{N_{d}}}\left\lbrack {u_{2m_{d}}\ u_{{2m_{d}} + 1}u_{{2m_{d}} + 2}u_{{2m_{d}} + 3}} \right\rbrack}},{{{if}N_{d}} \geq N_{e}}$e = {1, 2} − d${W_{m_{d}}^{(1)} = {\frac{1}{\sqrt{N_{d}}}\left\lbrack {u_{2m_{d}}\ u_{{2m_{d}} + 1}} \right\rbrack}},$if N_(d) < N_(e) e = {1, 2} − d 4${0,1,_{}\ldots,\frac{O_{d}N_{d}}{2}} - 1$${W_{m_{d}}^{(1)} = {\frac{1}{\sqrt{N_{d}}}\left\lbrack {u_{2m_{d}}u_{{2m_{d}} + 1}u_{{2m_{d}} + 2}u_{{2m_{d}} + 3}} \right\rbrack}},$e = {1, 2} − d ${W_{m_{d}}^{(1)} = \frac{u_{2m_{d}}}{\sqrt{N_{d}}}},$ ifN_(d) < N_(e) e = {1, 2} − d

In yet another example of 4, the co-pol codebook is rank >1 and thecorresponding PMI indicates orthogonal beam groups. An example of such arank-2 codebook is shown in Table 42, where the dimension d=1, 2, andthe type of beam group is indicated by the higher layer RRC parameterCodebook-Config. An example of values for parameters (s₁, s₂) and (p₁,p₂) in the Table is shown in Table 43.

TABLE 43 Example parameter values Codebook-Config (s₁, s₂) (p₁, p₂) 1(1, 1) (−, −) 2 $\left( {\frac{O_{1}}{2},\frac{O_{2}}{2}} \right)$$\left( {\frac{O_{2}}{4},\frac{O_{2}}{4}} \right)$ 3$\left( {O_{1},\frac{O_{2}}{2}} \right)$$\left( {\frac{O_{2}}{4},\frac{O_{2}}{4}} \right)$ 4$\left( {O_{1},\frac{O_{2}}{4}} \right)$$\left( {\frac{O_{2}}{4},—} \right)$

TABLE 44 W₁ Co-pol Codebook for 2-layer CSI reporting using antennaports 15 to 14 + P N1, N2 > 1 m_(d) Precoder Value of Codebook-Config: 10, 1, . . . , O_(d)N_(d) − 1$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{m_{d}}\ u_{m_{d} + O_{d}}} \right\rbrack}$Value of Codebook-Config: 2${0,1,_{}\ldots,\frac{O_{d}N_{d}}{s_{d}}} - 1$$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{s_{d}m_{d}}\ u_{{s_{d}m_{d}} + p_{d}}\ u_{{s_{d}m_{d}} + O_{d}}\ u_{{s_{d}m_{d}} + O_{d} + p_{d}}} \right\rbrack}$Value of Codebook-Config: 3${0,1,_{}\ldots,\frac{O_{d}N_{d}}{s_{d}}} - 1$$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{s_{d}m_{d}}\ u_{{s_{d}m_{d}} + p_{d}}\ u_{{s_{d}m_{d}} + {2p_{d}}}\ u_{{s_{d}m_{d}} + {3p_{d}}}u_{{s_{d}m_{d}} + O_{d}}u_{{s_{d}m_{d}} + O_{d} + p_{d}}u_{{s_{d}m_{d}} + O_{d} + {2p_{d}}}u_{{s_{d}m_{d}} + O_{d} + {3p_{d}}}} \right\rbrack}$if N_(d) ≥ N_(e) e = {1, 2} − d${W_{m_{d}}^{(1)} = {\frac{1}{\sqrt{N_{d}}}\left\lbrack {u_{s_{d}m_{d}}\ u_{{s_{d}m_{d}} + 1}} \right\rbrack}},$if N_(d) < N_(e) e = {1, 2} − d Value of Codebook-Config: 4${0,1,_{}\ldots,\frac{O_{d}N_{d}}{s_{d}}} - 1$$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{s_{d}m_{d}}\ u_{{s_{d}m_{d}} + p_{d}}\ u_{{s_{d}m_{d}} + {2p_{d}}}\ u_{{s_{d}m_{d}} + {3p_{d}}}u_{{s_{d}m_{d}} + O_{d}}u_{{s_{d}m_{d}} + O_{d} + p_{d}}u_{{s_{d}m_{d}} + O_{d} + {2p_{d}}}u_{{s_{d}m_{d}} + O_{d} + {3p_{d}}}} \right\rbrack}$if N_(d) ≥ N_(e) e = {1, 2} − d${W_{m_{d}}^{(1)} = \frac{u_{s_{d}m_{d}}}{\sqrt{N_{d}}}},$ if N_(d) <N_(e) e = {1, 2} − d N₁ or N₂ = 1 m_(d) Precoder Value ofCodebook-Config: 1 0, 1, . . . , O_(d)N_(d) − 1$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{m_{d}}u_{m_{d} + O_{d}}} \right\rbrack}$O_(d)N_(d), O_(d)N_(d) + 1, . . . , 2O_(d)N_(d) − 1$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{m_{d}}u_{m_{d} + {2O_{d}}}} \right\rbrack}$2O_(d)N_(d), O_(d)N_(d) + 1, . . . , 3O_(d)N_(d) − 1$W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{m_{d}}u_{m_{d} + {3O_{d}}}} \right\rbrack}$Value of Codebook-Config: 4${m_{d}:0,1,_{}\ldots,\frac{O_{d}N_{d}}{s_{d}}} - 1$${W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{s_{d}m_{d}}\ u_{{s_{d}m_{d}} + p_{d}}\ u_{{s_{d}m_{d}} + {2p_{d}}}\ u_{{s_{d}m_{d}} + {3p_{d}}}u_{{s_{d}m_{d}} + O_{d}}u_{{s_{d}m_{d}} + O_{d} + p_{d}}u_{{s_{d}m_{d}} + O_{d} + {2p_{d}}}u_{{s_{d}m_{d}} + O_{d} + {3p_{d}}}} \right\rbrack}},$if N_(d) ≥ N_(e) e = {1, 2} − d${W_{m_{d}}^{(1)} = \frac{u_{s_{d}m_{d}}}{\sqrt{N_{d}}}},$ if N_(d) <N_(e) e = {1, 2} − d${m_{d}:\frac{O_{d}N_{d}}{s_{d}}},{\frac{O_{d}N_{d}}{s_{d}} + {1,_{}\ldots,\frac{2O_{d}N_{d}}{s_{d}}} - 1}$${W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{s_{d}m_{d}}\ u_{{s_{d}m_{d}} + p_{d}}\ u_{{s_{d}m_{d}} + {2p_{d}}}\ u_{{s_{d}m_{d}} + {3p_{d}}}u_{{s_{d}m_{d}} + {2O_{d}}}u_{{s_{d}m_{d}} + {2O_{d}} + p_{d}}u_{{s_{d}m_{d}} + {2O_{d}} + {2p_{d}}}u_{{s_{d}m_{d}} + {2O_{d}} + {3p_{d}}}} \right\rbrack}},$if N_(d) ≥ N_(e) e = {1, 2} − d${W_{m_{d}}^{(1)} = \frac{u_{s_{d}m_{d}}}{\sqrt{N_{d}}}},$ if N_(d) <N_(e) e = {1, 2} − d${m_{d}:\frac{2O_{d}N_{d}}{s_{d}}},{\frac{2O_{d}N_{d}}{s_{d}} + {1,_{}\ldots,\frac{3O_{d}N_{d}}{s_{d}}} - 1}$${W_{m_{d}}^{(2)} = {\frac{1}{\sqrt{2N_{d}}}\left\lbrack {u_{s_{d}m_{d}}\ u_{{s_{d}m_{d}} + p_{d}}\ u_{{s_{d}m_{d}} + {2p_{d}}}\ u_{{s_{d}m_{d}} + {3p_{d}}}u_{{s_{d}m_{d}} + {3O_{d}}}u_{{s_{d}m_{d}} + {3O_{d}} + p_{d}}u_{{s_{d}m_{d}} + {3O_{d}} + {2p_{d}}}u_{{s_{d}m_{d}} + {3O_{d}} + {3p_{d}}}} \right\rbrack}},$if N_(d) ≥ N_(e) e = {1, 2} − d${W_{m_{d}}^{(1)} = \frac{u_{s_{d}m_{d}}}{\sqrt{N_{d}}}},$ if N_(d) <N_(e) e = {1, 2} − d

In some embodiments, in the case of 1st Class B eMIMO-Type with K₁=2CSI-RS resources, two RIs can be reported in two CSI reports associatedwith the two CSI-RS resources. Let us denote the two RIs as RI^((1,1))and RI^((1,2)). In one example of 2-b-a, RI^((1,1)) and RI^((1,2)) arenot reported. There are two sub-alternatives: RI^((1,1)) and RI^((1,2))are fixed, for example RI^((1,1))=RI^((1,2))=1 or 8, or RI^((1,1))=1,RI^((1,2))=8, or RI^((1,1))=8, RI^((1,2))=1; and RI^((1,1)) andRI^((1,2)) are configured (via RRC signaling). In another example of2-b-b, only RI^((1,1)) is reported, where the reported RI^((1,1)) caneither be: restricted, for example to rank {1, 2} for co-pol and {1, 3}for dual-pol (1-bit RI^((1,1))), or {1, 2, 3, 4} for co-pol and {1, 3,5, 7} for dual-pol (2-bit RI^((1,1))); or unrestricted, for example torank 1-8 (3-bit RI^((1,1))). In yet another example, there are twosub-alternatives for RI^((1,2)): RI^((1,2)) is fixed, for example,RI^((1,2))=1 or 8; and RI^((1,2)) is configured (via RRC signaling). Inyet another example of 2-b-c: Only RI^((1,2)) is reported, where thereported RI^((1,2)) can either be: restricted, for example to rank {1,2}for co-pol and {1,3} for dual-pol (1-bit RI^((1,2))), or {1, 2, 3, 4}for co-pol and {1, 3, 5, 7} for dual-pol (2-bit RI^((1,2))); orunrestricted, for example to rank 1-8 (3-bit RI^((1,2))), where thereare two sub-alternatives for RI^((1,1)): RI^((1,1)) is fixed, forexample, RI^((1,1))=1 or 8; and RI^((1,1)) is configured (via RRCsignaling). In yet another example of 2-b-d, both RI^((1,1)) andRI^((1,2)) are reported, where one or both of them are restricted orunrestricted. Two examples of rank configurations in this case are shownin Table 45 and Table 46. Note that the maximum rank depends on theantenna port layouts (i.e., N₁, N₂ values) and the type of codebook(co-pol or dual-pol). In general, the maximum rank is N_(d) for co-poland 2N_(d) for dual-pol where d=1, 2.

TABLE 45 Example rank combinations for (N₁, N₂) = (8, 2) RankRI^((1, 1)) RI^((1, 2)) config. Type Co-pol Dual-pol #bits Type Co-pol#bits Dual-pol #bits 0 Restricted {1, 2} {1, 3} 1 Restricted {1, 2} 1{1, 3} 1 1 {1, 2, {1, 3, 2 3, 4} 5, 7} 2 Restricted {1, 2} {1, 3} 1Unrestricted {1, 2} 1 {1, 2, 2 3 {1, 2, {1, 3, 2 3, 4} 3, 4} 5, 7} 4Unrestricted {1, 2, {1, 2, 3 Restricted {1, 2} 1 {1, 3} 1 . . . , 8} . .. , 8} 5 Unrestricted {1, 2, {1, 2, 3 Unrestricted {1, 2} 1 {1, 2, 2 . .. , 8} . . . , 8} 3, 4}

TABLE 46 Example rank combinations (N₁, N₂) = (8, 8) Rank RI^((1, 1))RI^((1, 2)) config. Type Co-pol Dual-pol #bits Type Co-pol Dual-pol#bits 0 Restricted {1, 2} {1, 3} 1 Restricted {1, 2} {1, 3} 1 1 {1, 2,{1, 3, 2 {1, 2} {1, 3} 1 3, 4} 5, 7} 2 {1, 2} {1, 3} 1 {1, 2, {1, 3, 23, 4} 5, 7} 3 {1, 2, {1, 3, 2 {1, 2, {1, 3, 2 3, 4} 5, 7} 3, 4} 5, 7} 4Restricted {1, 2} {1, 3} 1 Unrestricted {1, 2, {1, 2, 3 5 {1, 2, {1, 3,2 . . . , 8} . . . , 8} 3, 4} 5, 7} 6 Unrestricted {1, 2, {1, 2, 3Restricted {1, 2} {1, 3} 1 7 . . . , 8} . . . , 8} {1, 2, {1, 3, 2 3, 4}5, 7} 8 Unrestricted {1, 2, {1, 2, 3 Unrestricted {1, 2, {1, 2, 3 . . ., 8} . . . , 8} . . . , 8} . . . , 8}

Note that for 1D antenna port layouts, only alternatives 2-b-a and 2-b-bare applicable (assuming antenna ports are in the 1st dimension). Theoverall rank of the 1st eMIMO-Type RI⁽¹⁾ depends on the reportedRI^((1,1)) and RI^((1,2)). For example, 1≤RI⁽¹⁾≤max(RI^((1,1)),RI^((1,2))). Once RI⁽¹⁾ is determined from RI^((1,1)) and RI^((1,2)),all embodiments mentioned earlier in the present disclosure on dependentand independent reporting of RI⁽¹⁾ and RI⁽²⁾ in Class A+Class B K=1eMIMO-Types are applicable.

The present disclosure covers the use of all the above configurations orsub-configurations. It also covers the use of only a subset of all theabove configurations or sub-configurations. If more than oneconfigurations or sub-configurations are used, the choice ofconfiguration or sub-configuration is performed via higher layersignaling.

For example, a subset of rank configurations is used to configure onehybrid configuration to the UE. An example of such a subset is shown inTable 47. As example use case for this is when the first dimension isco-polarized and the second dimension is dual-polarized. The number ofconfigurations in the Table is 2, so 1-bit RRC signaling is required toconfigure one of the two rank configurations.

TABLE 47 Configurable rank configurations Rank RI^((1, 1)) RI^((1, 2))configuration Type Co-pol #bits Type Dual-pol #bits 0 Restricted {1, 2}1 Restricted {1, 3} 1 1 {1, 2} 1 {1, 3, 2 5, 7}

A variation of the above example where only one rank configuration issupported_can be described as follows. Two examples are given in Table48 and Table 49 below where the number of bits for RI^((1,2)) is 1 and2, respectively. In this case, an additional RRC parameter is notneeded.

TABLE 48 Configurable rank configurations: RI^((1, 2)) = 1 RI^((1, 1))RI^((1, 2)) Type Co-pol #bits Type Dual-pol #bits Restricted {1, 2} 1Restricted {1, 3} 1

TABLE 49 Configurable rank configurations: RI^((1, 2)) = 2 RI^((1, 1))RI^((1, 2)) Type Co-pol #bits Type Dual-pol #bits Restricted {1, 2} 1Restricted {1, 3, 5, 7} 2

In some embodiments, in the case of 1st Class B eMIMO-Type with K₁>1CSI-RS resources, K₁ RIs can be reported in K₁ CSI reports associatedwith the K₁ CSI-RS resources. Let us denote the two RIs as RI^((1,1)),RI^((1,2)), . . . , RI^((1,K1)). In one example of 2-b-a, RI^((1,1)),RI^((1,2)), . . . , RI^((1,K1)) are not reported. There are twosub-alternatives: RI^((1,1)), RI^((1,2)), . . . , RI^((1,K1)) are fixed,for example all of them are 1 or 8, or a subset (S₁) of reported RIs isfixed to 1 and another subset (S₂) to 8 where S₁ and S₂ are disjoint andtheir union covers all RIs; and RI^((1,1)), RI^((1,2)), . . . ,RI^((1,K1)) are configured (via RRC signaling). In another example of2-b-b, only a subset (S₁) of RIs is reported, where the reportedRI^((1,x)) for x in S₁ can either be: restricted, for example to rank{1, 2} for co-pol and {1, 3} for dual-pol (1-bit RI^((1,x))), or {1, 2,3, 4} for co-pol and {1, 3, 5, 7} for dual-pol (2-bit RI^((1,x))); orunrestricted, for example to rank 1-8 (3-bit RI^((1,x))). Also,RI^((1,x))s for all x in S₁ are either the same or can be different.There are two sub-alternatives for RI^((1,y)) for y not in S₁:RI^((1,y)) is fixed, for example, 1 or 8; and RI^((1,y)) is configured(via RRC signaling). Also, RI^((1,y))s for all y not in S₁ are eitherthe same or can be different. In yet another example of 2-b-d, all ofRI^((1,1)), RI^((1,2)), . . . , RI^((1,K1)) are reported, where some orall of them are restricted or unrestricted. When the reported RI^((1,y))for y in {1, 2, . . . , K₁} is restricted, the reported RI^((1,y)) canbe 1 bit indicating rank {1, 3} or {1, 2} or 2 bits indicating rank {1,3, 5, 7} or {1, 2, 3, 4}. When the reported RI is unrestricted, them allpossible ranks can be reported. For example, the reported RI can be 3bits indicating rank 1-8.

The codebooks for RI^((1,1)), RI^((1,2)), . . . , RI^((1,K1)) reportingcan be legacy (up to Rel. 13) codebooks or the co-pol codebook proposedin the present disclosure.

In some embodiments, a UE is configured with a hybrid CSI reporting inwhich the 1st eMIMO-Type is Class B, K₁=1 with N_(P1) ports and the 2ndeMIMO-Type is Class B, K₂=1 with N_(P2) ports, where N_(P1), N_(P2)=2,4, 8. The CSI reported in the first Class B eMIMO-Type is either:alternative 1-a (Table 13): PMI or alternative 1-b (Table 13): CQI,RI⁽¹⁾, PMI and that reported in the 2nd Class B eMIMO-Type includesRI⁽²⁾, CQI, and PMI. The codebooks for the two eMIMO-Types can beaccording to one of the following alternatives: alt0: Rel. 13 Class Bcodebook; and alt1: One of Rel. 12 codebooks. There are two alternativesfor configuring N_(P1), N_(P2): N_(P1)=N_(P2); and N_(P1)≠N_(P2).

Depending on whether both or at least one of RI⁽¹⁾ and RI⁽²⁾ arereported, there may be following alternatives (as shown in Table 13):1-a: Only RI⁽¹⁾ is reported; 1-b: Only RI⁽²⁾ is reported; and 1-c: BothRI⁽¹⁾ and RI⁽²⁾ are reported. All embodiments on RI reportingalternatives (alternatives 0-a, 0-b, 0-c) for the case of Class A+ClassB K=1 described earlier in the present disclosure are applicable in thiscase too.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

None of the description in this application should be read as implyingthat any particular element, step, or function is an essential elementthat must be included in the claims scope. The scope of patented subjectmatter is defined only by the claims. Moreover, none of the claims areintended to invoke 35 U.S.C. § 112(f) unless the exact words “means for”are followed by a participle.

What is claimed is:
 1. A user equipment (UE), comprising: a transceiverconfigured to receive information about a CSI report; and a processor,operably coupled to the transceiver, configured to determine a precodingmatrix indicator (PMI) indicating a total of N₃ precoding matrices basedon a weighted sum using L pairs (w_(i), c_(i)), where i=1, . . . , L,w_(i) corresponds to a joint basis vector across spatial and frequencydimensions, and c_(i) corresponds to a coefficient, wherein thetransceiver is further configured to transmit the CSI report includingthe PMI.
 2. The UE of claim 1, wherein: the PMI includes at least threeindicators: a first indicator indicating L joint basis vectors, a secondindicator indicating L amplitudes, and a third indicator indicating Lphases, and c_(i)=m_(i)×p_(i), where m_(i) is amplitude and p_(i) isphase.
 3. The UE of claim 1, wherein each joint basis vector w_(i)comprises a pair of vectors (a_(i), b_(i)), a first vector a_(i)corresponds to the spatial dimension and a second vector b_(i)corresponds to the frequency dimension.
 4. The UE of claim 3, wherein alength of the second vector b_(i) is N₃, b_(i)=[b_(i,0) b_(i,1) . . .b_(i,N) ₃ ⁻¹], and w_(i)=[a_(i)b_(i,0), a_(i)b_(i,1), . . . a_(i)b_(i,N)₃ ⁻¹].
 5. The UE of claim 3, wherein the spatial dimension is associatedwith a two-dimensional antenna port layout comprising N₁ antenna portsin a first antenna port dimension and N₂ antenna ports in a secondantenna port dimension, and a size of the first vector a_(i) is N₁N₂×1.6. The UE of claim 3, wherein the first and second vectors are discreteFourier transform (DFT) vectors.
 7. The UE of claim 3, wherein the N₃precoding matrices are based on an equation including the weighted sumΣ_(i=0) ^(L-1)(c_(i)w_(i)).
 8. A base station, comprising: a transceiverconfigured to transmit information about a CSI report, and receive theCSI report including a precoding matrix indicator (PMI); and aprocessor, operably coupled to the transceiver, configured to determinethe PMI from the CSI report, wherein the PMI indicates a total of N₃precoding matrices based on a weighted sum using L pairs (w_(i), c_(i)),where i=1, . . . , L, w_(i) corresponds to a joint basis vector acrossspatial and frequency dimensions, and c_(i) corresponds to acoefficient.
 9. The base station of claim 8, wherein: the PMI includesat least three indicators: a first indicator indicating L joint basisvectors, a second indicator indicating L amplitudes, and a thirdindicator indicating L phases, and c_(i)=m_(i)×p_(i), where m_(i) isamplitude and p_(i) is phase.
 10. The base station of claim 8, whereineach joint basis vector w_(i) comprises a pair of vectors (a_(i),b_(i)), a first vector a_(i) corresponds to the spatial dimension and asecond vector b_(i) corresponds to the frequency dimension.
 11. The basestation of claim 10, wherein a length of the second vector b_(i) is N₃,b_(i)=[b_(i,0) b_(i,1) . . . b_(i,N) ₃ ⁻¹], and w_(i)=[a_(i)b_(i,0),a_(i)b_(i,1), . . . a_(i)b_(i,N) ₃ ⁻¹].
 12. The base station of claim10, wherein the spatial dimension is associated with a two-dimensionalantenna port layout comprising N₁ antenna ports in a first antenna portdimension and N₂ antenna ports in a second antenna port dimension, and asize of the first vector a_(i) is N₁N₂×1.
 13. The base station of claim10, wherein the first and second vectors are discrete Fourier transform(DFT) vectors.
 14. The base station of claim 10, wherein the N₃precoding matrices are based on an equation including the weighted sumΣ_(i=0) ^(L-1)(c_(i)w_(i)).
 15. A method of operating a user equipment(UE), the method comprising: receiving information about a CSI report;determining a precoding matrix indicator (PMI) indicating a total of N₃precoding matrices based on a weighted sum using L pairs (w_(i), c_(i)),where i=1, . . . , L, w_(i) corresponds to a joint basis vector acrossspatial and frequency dimensions, and c_(i) corresponds to acoefficient; and transmitting the CSI report including the PMI.
 16. Themethod of claim 15, wherein: the PMI includes at least three indicators:a first indicator indicating L joint basis vectors, a second indicatorindicating L amplitudes, and a third indicator indicating L phases, andc_(i)=m_(i)×p_(i), where m_(i) is amplitude and p_(i) is phase.
 17. Themethod of claim 15, wherein each joint basis vector w_(i) comprises apair of vectors (a_(i), b_(i)), a first vector a_(i) corresponds to thespatial dimension and a second vector b_(i) corresponds to the frequencydimension.
 18. The method of claim 17, wherein a length of the secondvector b_(i) is N₃, b_(i)=[b_(i,0) b_(i,1) . . . b_(i,N) ₃ ⁻¹], andw_(i)=[a_(i)b_(i,0), a_(i)b_(i,1), . . . a_(i)b_(i,N) ₃ ⁻¹].
 19. Themethod of claim 17, wherein the spatial dimension is associated with atwo-dimensional antenna port layout comprising N₁ antenna ports in afirst antenna port dimension and N₂ antenna ports in a second antennaport dimension, and a size of the first vector a_(i) is N₁N₂×1.
 20. Themethod of claim 17, wherein the first and second vectors are discreteFourier transform (DFT) vectors.